CVE-2021-47277

一、漏洞信息
 漏洞编号：[CVE-2021-47277](https://nvd.nist.gov/vuln/detail/CVE-2021-47277)
 漏洞归属组件：[kernel](https://gitee.com/src-openeuler/kernel)
 漏洞归属的版本：4.19.140,4.19.194,4.19.90,5.10.0,6.1.0,6.1.14,6.1.19,6.1.5,6.1.6,6.1.8,6.4.0,6.6.0
 CVSS V3.0分值：
  BaseScore：0.0 None
  Vector：CVSS：3.0/
 漏洞简述：
  In the Linux kernel, the following vulnerability has been resolved:kvm: avoid speculation-based attacks from out-of-range memslot accessesKVM s mechanism for accessing guest memory translates a guest physicaladdress (gpa) to a host virtual address using the right-shifted gpa(also known as gfn) and a struct kvm_memory_slot.  The translation isperformed in __gfn_to_hva_memslot using the following formula:      hva = slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZEIt is expected that gfn falls within the boundaries of the guest sphysical memory.  However, a guest can access invalid physical addressesin such a way that the gfn is invalid.__gfn_to_hva_memslot is called from kvm_vcpu_gfn_to_hva_prot, which firstretrieves a memslot through __gfn_to_memslot.  While __gfn_to_memslotdoes check that the gfn falls within the boundaries of the guest sphysical memory or not, a CPU can speculate the result of the check andcontinue execution speculatively using an illegal gfn. The speculationcan result in calculating an out-of-bounds hva.  If the resulting hostvirtual address is used to load another guest physical address, thisis effectively a Spectre gadget consisting of two consecutive reads,the second of which is data dependent on the first.Right now it s not clear if there are any cases in which this isexploitable.  One interesting case was reported by the original authorof this patch, and involves visiting guest page tables on x86.  Rightnow these are not vulnerable because the hva read goes through get_user(),which contains an LFENCE speculation barrier.  However, there arepatches in progress for x86 uaccess.h to mask kernel addresses instead ofusing LFENCE; once these land, a guest could use speculation to readfrom the VMM s ring 3 address space.  Other architectures such as ARMalready use the address masking method, and would be susceptible tothis same kind of data-dependent access gadgets.  Therefore, this patchproactively protects from these attacks by masking out-of-bounds gfnsin __gfn_to_hva_memslot, which blocks speculation of invalid hvas.Sean Christopherson noted that this patch does not coverkvm_read_guest_offset_cached.  This however is limited to a few bytespast the end of the cache, and therefore it is unlikely to be useful inthe context of building a chain of data dependent accesses.
 漏洞公开时间：2024-05-21 23:15:16
 漏洞创建时间：2024-05-21 17:28:40
 漏洞详情参考链接：
  https://nvd.nist.gov/vuln/detail/CVE-2021-47277
<details>
<summary>更多参考(点击展开)</summary>

| 参考来源 | 参考链接 | 来源链接 |
| ------- | -------- | -------- |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/22b87fb17a28d37331bb9c1110737627b17f6781 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/3098b86390a6b9ea52657689f08410baf130ceff |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/361ce3b917aff93123e9e966d8608655c967f438 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/740621309b25bbf619b8a0ba5fd50a8e58989441 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/7af299b97734c7e7f465b42a2139ce4d77246975 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/bff1fbf0cf0712686f1df59a83fba6e31d2746a0 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/da27a83fd6cc7780fea190e1f5c19e87019da65c |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/ed0e2a893092c7fcb4ff7ba74e5efce53a6f5940 |  |
| suse_bugzilla | http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-47277 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://www.cve.org/CVERecord?id=CVE-2021-47277 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/22b87fb17a28d37331bb9c1110737627b17f6781 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/3098b86390a6b9ea52657689f08410baf130ceff | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/361ce3b917aff93123e9e966d8608655c967f438 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/740621309b25bbf619b8a0ba5fd50a8e58989441 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/7af299b97734c7e7f465b42a2139ce4d77246975 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/bff1fbf0cf0712686f1df59a83fba6e31d2746a0 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/da27a83fd6cc7780fea190e1f5c19e87019da65c | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/stable/c/ed0e2a893092c7fcb4ff7ba74e5efce53a6f5940 | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| suse_bugzilla | https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2021/CVE-2021-47277.mbox | https://bugzilla.suse.com/show_bug.cgi?id=1224960 |
| redhat_bugzilla | https://lore.kernel.org/linux-cve-announce/2024052152-CVE-2021-47277-68e4@gregkh/T | https://bugzilla.redhat.com/show_bug.cgi?id=2282520 |
| ubuntu | https://www.cve.org/CVERecord?id=CVE-2021-47277 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/linus/da27a83fd6cc7780fea190e1f5c19e87019da65c (5.13-rc6) | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/3098b86390a6b9ea52657689f08410baf130ceff | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/740621309b25bbf619b8a0ba5fd50a8e58989441 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/361ce3b917aff93123e9e966d8608655c967f438 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/22b87fb17a28d37331bb9c1110737627b17f6781 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/bff1fbf0cf0712686f1df59a83fba6e31d2746a0 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/7af299b97734c7e7f465b42a2139ce4d77246975 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/ed0e2a893092c7fcb4ff7ba74e5efce53a6f5940 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://git.kernel.org/stable/c/da27a83fd6cc7780fea190e1f5c19e87019da65c | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://nvd.nist.gov/vuln/detail/CVE-2021-47277 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://launchpad.net/bugs/cve/CVE-2021-47277 | https://ubuntu.com/security/CVE-2021-47277 |
| ubuntu | https://security-tracker.debian.org/tracker/CVE-2021-47277 | https://ubuntu.com/security/CVE-2021-47277 |

</details>

漏洞分析指导链接：
  https://gitee.com/openeuler/cve-manager/blob/master/cve-vulner-manager/doc/md/manual.md
 漏洞数据来源:
  openBrain开源漏洞感知系统
 漏洞补丁信息：
  <details>
<summary>详情(点击展开)</summary>

| 影响的包 | 修复版本 | 修复补丁 | 问题引入补丁 | 来源  |
| ------- | -------- | ------- | -------- | --------- |
| linux |  | https://git.kernel.org/linus/da27a83fd6cc7780fea190e1f5c19e87019da65c | 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:kvm: avoid speculation-based attacks from out-of-range memslot accessesKVM s mechanism for accessing guest memory translates a guest physicaladdress (gpa) to a host virtual address using the right-shifted gpa(also known as gfn) and a struct kvm_memory_slot.  The translation isperformed in __gfn_to_hva_memslot using the following formula:      hva = slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZEIt is expected that gfn falls within the boundaries of the guest sphysical memory.  However, a guest can access invalid physical addressesin such a way that the gfn is invalid.__gfn_to_hva_memslot is called from kvm_vcpu_gfn_to_hva_prot, which firstretrieves a memslot through __gfn_to_memslot.  While __gfn_to_memslotdoes check that the gfn falls within the boundaries of the guest sphysical memory or not, a CPU can speculate the result of the check andcontinue execution speculatively using an illegal gfn. The speculationcan result in calculating an out-of-bounds hva.  If the resulting hostvirtual address is used to load another guest physical address, thisis effectively a Spectre gadget consisting of two consecutive reads,the second of which is data dependent on the first.Right now it s not clear if there are any cases in which this isexploitable.  One interesting case was reported by the original authorof this patch, and involves visiting guest page tables on x86.  Rightnow these are not vulnerable because the hva read goes through get_user(),which contains an LFENCE speculation barrier.  However, there arepatches in progress for x86 uaccess.h to mask kernel addresses instead ofusing LFENCE; once these land, a guest could use speculation to readfrom the VMM s ring 3 address space.  Other architectures such as ARMalready use the address masking method, and would be susceptible tothis same kind of data-dependent access gadgets.  Therefore, this patchproactively protects from these attacks by masking out-of-bounds gfnsin __gfn_to_hva_memslot, which blocks speculation of invalid hvas.Sean Christopherson noted that this patch does not coverkvm_read_guest_offset_cached.  This however is limited to a few bytespast the end of the cache, and therefore it is unlikely to be useful inthe context of building a chain of data dependent accesses.
 openEuler评分：
  5.5
 Vector：CVSS：3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
 受影响版本排查(受影响/不受影响)：
  1.openEuler-20.03-LTS-SP4(4.19.90):受影响
2.openEuler-22.03-LTS-SP1(5.10.0):不受影响
3.openEuler-22.03-LTS-SP3(5.10.0):不受影响
4.openEuler-22.03-LTS-SP4(5.10.0):不受影响
5.master(6.6.0):不受影响
6.openEuler-24.03-LTS(6.6.0):不受影响
7.openEuler-24.03-LTS-Next(6.6.0):不受影响

修复是否涉及abi变化(是/否)：
  1.openEuler-20.03-LTS-SP4(4.19.90):否
2.openEuler-22.03-LTS-SP1(5.10.0):否
3.openEuler-22.03-LTS-SP3(5.10.0):否
4.master(6.6.0):否
5.openEuler-24.03-LTS(6.6.0):否
6.openEuler-24.03-LTS-Next(6.6.0):否
7.openEuler-22.03-LTS-SP4(5.10.0):否

原因说明：
  1.master(6.6.0):
2.openEuler-20.03-LTS-SP4(4.19.90):
3.openEuler-22.03-LTS-SP1(5.10.0):
4.openEuler-22.03-LTS-SP3(5.10.0):
5.openEuler-22.03-LTS-SP4(5.10.0):
6.openEuler-24.03-LTS(6.6.0):
7.openEuler-24.03-LTS-Next(6.6.0):

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