In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
IntheLinux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won't touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I'm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won't touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In theLinux kernel, the following vulnerability hasbeen resolved:swiotlb: fixinfo leak withDMA_FROM_DEVICEThe problem I'm addressing was discovered bythe LTP test coveringcve-2018-1000204.A short description of what happens follows:1) Thetest case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len ==524288, dxdfer_dir == SG_DXFER_FROM_DEV and a correspondingdxferp. The peculiarthing about this is that TUR is not reading from thedevice.2) In sg_start_req() theinvocation of blk_rq_map_user() effectively bounces the user-spacebuffer. As if the device was totransfer into it. Sincecommit a45b599ad808 ("scsi: sg:allocate with __GFP_ZERO in sg_build_indirect()") we make sure this firstbounce buffer is allocated with GFP_ZERO.3) Forthe rest ofthe story wekeep ignoring that we have a TUR, so the devicewon't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsidevice and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics).This mapping involves bouncing viathe swiotlb (we need swiotlb todo virtio in protected guestlike s390 Secure Execution, or AMDSEV).4) When the SCSITUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previousIO data), to the firstbounce buffer,whichcontains all zeros. Then we copy back the content of the firstbounce buffer to theuser-space buffer.5)The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails.One can argue thatthis isan swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copyingthecontent of theoriginal bufferinto the swiotlb buffer istheonly wayI can think of to make swiotlb transparent in suchscenarios. So let's do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.The Linux kernel CVE team has assigned CVE-2022-48853 to this issue.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
IntheLinuxkernel,thefollowingvulnerabilityhas been resolved:swiotlb: fix info leak withDMA_FROM_DEVICEThe problemI m addressingwas discovered by the LTP test coveringcve-2018-1000204.A shortdescription of what happens follows:1) The test case issues a command code 00 (TEST UNITREADY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is thatTUR is not readingfrom the device.2) In sg_start_req() the invocation ofblk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with__GFP_ZERO in sg_build_indirect()) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For therest of the storywe keep ignoring that we have aTUR, so the device wont touch the buffer we prepare as if the wehad a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by thefunction virtqueue_add_split() which uses DMA_FROM_DEVICE for thein sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlbto do virtio in protected guestlike s390 Secure Execution, or AMDSEV).4) When the SCSI TUR isdone,we first copy back the contentof the second (thatis swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back thecontent of thefirstbounce bufferto theuser-space buffer.5) The test case detectsthat the buffer,whichit zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros,and theswiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe onlywayI can think ofto make swiotlbtransparent in suchscenarios.So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem Imaddressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues acommand code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and acorresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 (scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have aTUR, so the device won t touch the buffer we prepare as if the we had aDMA_FROM_DEVICE type of situation. My setup uses avirtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain tall zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in asense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way Ican think of to make swiotlb transparent in suchscenarios. So let sdo just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problemIm addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issuesa command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV anda corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we havea TUR, so the device won t touch the buffer we prepare as if the we hada DMA_FROM_DEVICE type of situation. My setup usesa virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, aint all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent ina sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only wayI can think of to make swiotlb transparent in suchscenarios. So lets do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
| linux | | https://git.kernel.org/linus/ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e | https://git.kernel.org/linus/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | ubuntu |
</details>
二、漏洞分析结构反馈
影响性分析说明：
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
In the Linux kernel, the following vulnerability has been resolved:swiotlb: fix info leak with DMA_FROM_DEVICEThe problem I m addressing was discovered by the LTP test coveringcve-2018-1000204.A short description of what happens follows:1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device.2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ( scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() ) we make sure this first bounce buffer is allocated with GFP_ZERO.3) For the rest of the story we keep ignoring that we have a TUR, so the device won t touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the in sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV).4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer.5) The test case detects that the buffer, which it zero-initialized, ain t all zeros and fails.One can argue that this is an swiotlb problem, because without swiotlbwe leak all zeros, and the swiotlb should be transparent in a sense thatit does not affect the outcome (if all other participants are wellbehaved).Copying the content of the original buffer into the swiotlb buffer isthe only way I can think of to make swiotlb transparent in suchscenarios. So let s do just that if in doubt, but allow the driverto tell us that the whole mapped buffer is going to be overwritten,in which case we can preserve the old behavior and avoid the performanceimpact of the extra bounce.
