KVM: nSVM: Remove a user-triggerable WARN on nested_svm_load_cr3() succeeding

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Summary

CVECVE-2026-43315
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-08 14:16:39 UTC
Updated2026-05-12 14:10:27 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: nSVM: Remove a user-triggerable WARN on nested_svm_load_cr3() succeeding Drop the WARN in svm_set_nested_state() on nested_svm_load_cr3() failing as it is trivially easy to trigger from userspace by modifying CPUID after loading CR3. E.g. modifying the state restoration selftest like so: --- tools/testing/selftests/kvm/x86/state_test.c +++ tools/testing/selftests/kvm/x86/state_test.c @@ -280,7 +280,16 @@ int main(int argc, char *argv[]) /* Restore state in a new VM. */ vcpu = vm_recreate_with_one_vcpu(vm); - vcpu_load_state(vcpu, state); + + if (stage == 4) { + state->sregs.cr3 = BIT(44); + vcpu_load_state(vcpu, state); + + vcpu_set_cpuid_property(vcpu, X86_PROPERTY_MAX_PHY_ADDR, 36); + __vcpu_nested_state_set(vcpu, &state->nested); + } else { + vcpu_load_state(vcpu, state); + } /* * Restore XSAVE state in a dummy vCPU, first without doing generates: WARNING: CPU: 30 PID: 938 at arch/x86/kvm/svm/nested.c:1877 svm_set_nested_state+0x34a/0x360 [kvm_amd] Modules linked in: kvm_amd kvm irqbypass [last unloaded: kvm] CPU: 30 UID: 1000 PID: 938 Comm: state_test Tainted: G W 6.18.0-rc7-58e10b63777d-next-vm Tainted: [W]=WARN Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:svm_set_nested_state+0x34a/0x360 [kvm_amd] Call Trace: <TASK> kvm_arch_vcpu_ioctl+0xf33/0x1700 [kvm] kvm_vcpu_ioctl+0x4e6/0x8f0 [kvm] __x64_sys_ioctl+0x8f/0xd0 do_syscall_64+0x61/0xad0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Simply delete the WARN instead of trying to prevent userspace from shoving "illegal" state into CR3. For better or worse, KVM's ABI allows userspace to set CPUID after SREGS, and vice versa, and KVM is very permissive when it comes to guest CPUID. I.e. attempting to enforce the virtual CPU model when setting CPUID could break userspace. Given that the WARN doesn't provide any meaningful protection for KVM or benefit for userspace, simply drop it even though the odds of breaking userspace are minuscule. Opportunistically delete a spurious newline.

Risk And Classification

EPSS: 0.000240000 probability, percentile 0.070210000 (date 2026-05-11)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd 155ec243ef726f4bc49536fa0bfb565dc011ab17 git Not specified
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd 580ea57840864d40e019bc13fd26afdc8d510a2f git Not specified
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b git Not specified
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd ce904c8a5bbe697eae0f7e34b07095bd7a6dee19 git Not specified
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd 969e5e13ff5c18603f21d1f9f64ec9194e141ac0 git Not specified
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8 git Not specified
CNA Linux Linux affected b222b0b88162bdef4eceb12a79d5edbbdb23dbfd fc3ba56385d03501eb582e4b86691ba378e556f9 git Not specified
CNA Linux Linux affected 5.14 Not specified
CNA Linux Linux unaffected 5.14 semver Not specified
CNA Linux Linux unaffected 5.15.202 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.165 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.128 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.75 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.16 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.6 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/580ea57840864d40e019bc13fd26afdc8d510a2f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fc3ba56385d03501eb582e4b86691ba378e556f9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/155ec243ef726f4bc49536fa0bfb565dc011ab17 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ce904c8a5bbe697eae0f7e34b07095bd7a6dee19 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/969e5e13ff5c18603f21d1f9f64ec9194e141ac0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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