一、漏洞信息
漏洞编号：CVE-2024-26976
漏洞归属组件：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 V2.0分值：
BaseScore：0.0 Low
Vector：CVSS：2.0/
漏洞简述：
In the Linux kernel, the following vulnerability has been resolved:KVM: Always flush async #PF workqueue when vCPU is being destroyedAlways flush the per-vCPU async #PF workqueue when a vCPU is clearing itscompletion queue, e.g. when a VM and all its vCPUs is being destroyed.KVM must ensure that none of its workqueue callbacks is running when thelast reference to the KVM module is put. Gifting a reference to theassociated VM prevents the workqueue callback from dereferencing freedvCPU/VM memory, but does not prevent the KVM module from being unloadedbefore the callback completes.Drop the misguided VM refcount gifting, as calling kvm_put_kvm() fromasync_pf_execute() if kvm_put_kvm() flushes the async #PF workqueue willresult in deadlock. async_pf_execute() can t return until kvm_put_kvm()finishes, and kvm_put_kvm() can t return until async_pf_execute() finishes: WARNING: CPU: 8 PID: 251 at virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm] Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Workqueue: events async_pf_execute [kvm] RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm] Call Trace: async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 ---[ end trace 0000000000000000 ]--- INFO: task kworker/8:1:251 blocked for more than 120 seconds. Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 echo 0 > /proc/sys/kernel/hung_task_timeout_secs disables this message. task:kworker/8:1 state:D stack:0 pid:251 ppid:2 flags:0x00004000 Workqueue: events async_pf_execute [kvm] Call Trace: __schedule+0x33f/0xa40 schedule+0x53/0xc0 schedule_timeout+0x12a/0x140 __wait_for_common+0x8d/0x1d0 __flush_work.isra.0+0x19f/0x2c0 kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm] kvm_arch_destroy_vm+0x78/0x1b0 [kvm] kvm_put_kvm+0x1c1/0x320 [kvm] async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 If kvm_clear_async_pf_completion_queue() actually flushes the workqueue,then there s no need to gift async_pf_execute() a reference because allinvocations of async_pf_execute() will be forced to complete before thevCPU and its VM are destroyed/freed. And that in turn fixes the moduleunloading bug as __fput() won t do module_put() on the last vCPU referenceuntil the vCPU has been freed, e.g. if closing the vCPU file also puts thelast reference to the KVM module.Note that kvm_check_async_pf_completion() may also take the work item offthe completion queue and so also needs to flush the work queue, as thework will not be seen by kvm_clear_async_pf_completion_queue(). Waitingon the workqueue could theoretically delay a vCPU due to waiting for thework to complete, but that s a very, very small chance, and likely a verysmall delay. kvm_arch_async_page_present_queued() unconditionally makes anew request, i.e. will effectively delay entering the guest, so theremaining work is really just: trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm);and mmput() can t drop the last reference to the page tables if the vCPU isstill alive, i.e. the vCPU won t get stuck tearing down page tables.Add a helper to do the flushing, specifically to deal with wakeup all work items, as they aren t actually work items, i.e. are never placed in aworkqueue. Trying to flush a bogus workqueue entry rightly makes__flush_work() complain (kudos to whoever added that sanity check).Note, commit 5f6de5cbebee ( KVM: Prevent module exit until al---truncated---
漏洞公开时间：2024-05-01 14:15:14
漏洞创建时间：2024-05-01 14:37:15
漏洞详情参考链接：
https://nvd.nist.gov/vuln/detail/CVE-2024-26976

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：

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: Always flush async #PF workqueue when vCPU is being destroyedAlways flush the per-vCPU async #PF workqueue when a vCPU is clearing itscompletion queue, e.g. when a VM and all its vCPUs is being destroyed.KVM must ensure that none of its workqueue callbacks is running when thelast reference to the KVM module is put. Gifting a reference to theassociated VM prevents the workqueue callback from dereferencing freedvCPU/VM memory, but does not prevent the KVM module from being unloadedbefore the callback completes.Drop the misguided VM refcount gifting, as calling kvm_put_kvm() fromasync_pf_execute() if kvm_put_kvm() flushes the async #PF workqueue willresult in deadlock. async_pf_execute() can t return until kvm_put_kvm()finishes, and kvm_put_kvm() can t return until async_pf_execute() finishes: WARNING: CPU: 8 PID: 251 at virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm] Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Workqueue: events async_pf_execute [kvm] RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm] Call Trace: async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 ---[ end trace 0000000000000000 ]--- INFO: task kworker/8:1:251 blocked for more than 120 seconds. Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 echo 0 > /proc/sys/kernel/hung_task_timeout_secs disables this message. task:kworker/8:1 state:D stack:0 pid:251 ppid:2 flags:0x00004000 Workqueue: events async_pf_execute [kvm] Call Trace: __schedule+0x33f/0xa40 schedule+0x53/0xc0 schedule_timeout+0x12a/0x140 __wait_for_common+0x8d/0x1d0 __flush_work.isra.0+0x19f/0x2c0 kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm] kvm_arch_destroy_vm+0x78/0x1b0 [kvm] kvm_put_kvm+0x1c1/0x320 [kvm] async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 If kvm_clear_async_pf_completion_queue() actually flushes the workqueue,then there s no need to gift async_pf_execute() a reference because allinvocations of async_pf_execute() will be forced to complete before thevCPU and its VM are destroyed/freed. And that in turn fixes the moduleunloading bug as __fput() won t do module_put() on the last vCPU referenceuntil the vCPU has been freed, e.g. if closing the vCPU file also puts thelast reference to the KVM module.Note that kvm_check_async_pf_completion() may also take the work item offthe completion queue and so also needs to flush the work queue, as thework will not be seen by kvm_clear_async_pf_completion_queue(). Waitingon the workqueue could theoretically delay a vCPU due to waiting for thework to complete, but that s a very, very small chance, and likely a verysmall delay. kvm_arch_async_page_present_queued() unconditionally makes anew request, i.e. will effectively delay entering the guest, so theremaining work is really just: trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm);and mmput() can t drop the last reference to the page tables if the vCPU isstill alive, i.e. the vCPU won t get stuck tearing down page tables.Add a helper to do the flushing, specifically to deal with wakeup all work items, as they aren t actually work items, i.e. are never placed in aworkqueue. Trying to flush a bogus workqueue entry rightly makes__flush_work() complain (kudos to whoever added that sanity check).Note, commit 5f6de5cbebee ( KVM: Prevent module exit until al---truncated---
openEuler评分：
5.5
Vector：CVSS：2.0/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-SP1(4.19.90):受影响
2.openEuler-20.03-LTS-SP4:受影响
3.openEuler-22.03-LTS(5.10.0):受影响
4.openEuler-22.03-LTS-SP1(5.10.0):受影响
5.openEuler-22.03-LTS-SP2(5.10.0):受影响
6.openEuler-22.03-LTS-SP3:受影响
7.openEuler-22.03-LTS-SP4:不受影响
8.master(6.1.0):不受影响
9.openEuler-22.03-LTS-Next(5.10.0):不受影响
10.openEuler-24.03-LTS(6.6.0):不受影响
11.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-SP1(4.19.90):否
2.openEuler-20.03-LTS-SP4:否
3.openEuler-22.03-LTS(5.10.0):否
4.openEuler-22.03-LTS-SP1(5.10.0):否
5.openEuler-22.03-LTS-SP2(5.10.0):否
6.openEuler-22.03-LTS-SP3:否
7.master(6.1.0):否
8.openEuler-22.03-LTS-Next(5.10.0):否
9.openEuler-24.03-LTS(6.6.0):否
10.openEuler-24.03-LTS-Next(6.6.0):否
11.openEuler-22.03-LTS-SP4:否

三、漏洞修复
安全公告链接：https://www.openeuler.org/zh/security/safety-bulletin/detail/?id=openEuler-SA-2024-1682