KVM: SVM: Add missing save/restore handling of LBR MSRs

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Summary

CVECVE-2026-46014
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-27 14:17:19 UTC
Updated2026-05-27 14:48:03 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Add missing save/restore handling of LBR MSRs MSR_IA32_DEBUGCTLMSR and LBR MSRs are currently not enumerated by KVM_GET_MSR_INDEX_LIST, and LBR MSRs cannot be set with KVM_SET_MSRS. So save/restore is completely broken. Fix it by adding the MSRs to msrs_to_save_base, and allowing writes to LBR MSRs from userspace only (as they are read-only MSRs) if LBR virtualization is enabled. Additionally, to correctly restore L1's LBRs while L2 is running, make sure the LBRs are copied from the captured VMCB01 save area in svm_copy_vmrun_state(). Note, for VMX, this also fixes a flaw where MSR_IA32_DEBUGCTLMSR isn't reported as an MSR to save/restore. Note #2, over-reporting MSR_IA32_LASTxxx on Intel is ok, as KVM already handles unsupported reads and writes thanks to commit b5e2fec0ebc3 ("KVM: Ignore DEBUGCTL MSRs with no effect") (kvm_do_msr_access() will morph the unsupported userspace write into a nop). [sean: guard with lbrv checks, massage changelog]

Risk And Classification

EPSS: 0.000170000 probability, percentile 0.042650000 (date 2026-06-01)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 24e09cbf480a72f9c952af4ca77b159503dca44b 2b922a42b531a82d7881add14a7698dcdc5e1f0a git Not specified
CNA Linux Linux affected 24e09cbf480a72f9c952af4ca77b159503dca44b 13a89ada5dcfc2539514c83ba5a2c61157f1ec6c git Not specified
CNA Linux Linux affected 24e09cbf480a72f9c952af4ca77b159503dca44b 3700f0788da6acf73b2df56690f4b201aa4aefd2 git Not specified
CNA Linux Linux affected 2.6.26 Not specified
CNA Linux Linux unaffected 2.6.26 semver Not specified
CNA Linux Linux unaffected 6.18.27 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.4 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/2b922a42b531a82d7881add14a7698dcdc5e1f0a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3700f0788da6acf73b2df56690f4b201aa4aefd2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/13a89ada5dcfc2539514c83ba5a2c61157f1ec6c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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