KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2024-40953
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-07-12 13:15:17 UTC
Updated2026-08-04 11:19:08 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the loads and stores are atomic. In the extremely unlikely scenario the compiler tears the stores, it's theoretically possible for KVM to attempt to get a vCPU using an out-of-bounds index, e.g. if the write is split into multiple 8-bit stores, and is paired with a 32-bit load on a VM with 257 vCPUs: CPU0 CPU1 last_boosted_vcpu = 0xff; (last_boosted_vcpu = 0x100) last_boosted_vcpu[15:8] = 0x01; i = (last_boosted_vcpu = 0x1ff) last_boosted_vcpu[7:0] = 0x00; vcpu = kvm->vcpu_array[0x1ff]; As detected by KCSAN: BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm] write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) value changed: 0x00000012 -> 0x00000000

Risk And Classification

Primary CVSS: v3.1 4.7 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-362

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary4.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.9HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
3.1CNADECLARED7.9HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 11a772d5376aa6d3e2e69b5b5c585f79b60c0e17 git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 4c141136a28421b78f34969b25a4fa32e06e2180 git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 71fbc3af3dacb26c3aa2f30bb3ab05c44d082c84 git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 82bd728a06e55f5b5f93d10ce67f4fe7e689853a git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 92c77807d938145c7c3350c944ef9f39d7f6017c git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 a937ef951bba72f48d2402451419d725d70dba20 git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 95c8dd79f3a14df96b3820b35b8399bd91b2be60 git Not specified
CNA Linux Linux affected 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 49f683b41f28918df3e51ddc0d928cb2e934ccdb git Not specified
CNA Linux Linux affected 2.6.39 Not specified
CNA Linux Linux unaffected 2.6.39 semver Not specified
CNA Linux Linux unaffected 4.19.323 4.19.* semver Not specified
CNA Linux Linux unaffected 5.4.285 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.228 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.169 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.96 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.36 6.6.* semver Not specified
CNA Linux Linux unaffected 6.9.7 6.9.* semver Not specified
CNA Linux Linux unaffected 6.10 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/92c77807d938145c7c3350c944ef9f39d7f6017c af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/4c141136a28421b78f34969b25a4fa32e06e2180 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/03/msg00002.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/95c8dd79f3a14df96b3820b35b8399bd91b2be60 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/a937ef951bba72f48d2402451419d725d70dba20 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/82bd728a06e55f5b5f93d10ce67f4fe7e689853a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/71fbc3af3dacb26c3aa2f30bb3ab05c44d082c84 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/49f683b41f28918df3e51ddc0d928cb2e934ccdb af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/11a772d5376aa6d3e2e69b5b5c585f79b60c0e17 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/01/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
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