perf/x86/amd/core: Avoid enabling BRS from the SVM reload path

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-72325
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 06:22:05 UTC
Updated2026-08-17 06:18:36 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: perf/x86/amd/core: Avoid enabling BRS from the SVM reload path Branch Sampling (BRS) and Last Branch Record (LBR) are mutually exclusive hardware features, and users of both are tracked via cpuc->lbr_users. When SVM is toggled on a CPU, the host perf events are reprogrammed to update the HostOnly filter bit (set when virtualization is enabled, cleared when it is disabled). On PerfMonV2-capable processors, this reprogramming is performed by calling amd_pmu_enable_all() to rewrite the event selectors. However, amd_pmu_enable_all() also calls amd_brs_enable_all(), which enables BRS whenever cpuc->lbr_users > 0. Having active LBR events satisfies this gating on processors that have LBR but not BRS. The kernel then tries to set the BRS enable bit in DebugExtnCfg (MSR 0xc000010f). Since that bit is deprecated on such hardware, the write results in a #GP: Call Trace: <IRQ> amd_pmu_enable_all+0x1d/0x90 amd_pmu_disable_virt+0x62/0xb0 kvm_arch_disable_virtualization_cpu+0xa/0x40 [kvm] hardware_disable_nolock+0x1a/0x30 [kvm] __flush_smp_call_function_queue+0x9b/0x410 __sysvec_call_function+0x18/0xc0 sysvec_call_function+0x69/0x90 </IRQ> <TASK> asm_sysvec_call_function+0x16/0x20 RIP: 0010:cpuidle_enter_state+0xc4/0x450 ? cpuidle_enter_state+0xb7/0x450 cpuidle_enter+0x29/0x40 cpuidle_idle_call+0xf5/0x160 do_idle+0x7b/0xe0 cpu_startup_entry+0x26/0x30 start_secondary+0x115/0x140 secondary_startup_64_no_verify+0x194/0x19b </TASK> Fix this by ensuring that BRS is not enabled from the event selector reprogramming path even when cpuc->lbr_users > 0.

Risk And Classification

EPSS: 0.002090000 probability, percentile 0.113510000 (date 2026-08-17)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected bae19fdd7e9e759580ac4693d2df3bc23ab415d7 e9b1a7411a667539c2f55e720bbb5f623b526a32 git Not specified
CNA Linux Linux affected bae19fdd7e9e759580ac4693d2df3bc23ab415d7 7cc438c99bba324a0562b1bafa747b10f7e251df git Not specified
CNA Linux Linux affected bae19fdd7e9e759580ac4693d2df3bc23ab415d7 46d0fd8535edce31f15e48d2de1bdee39a4850e5 git Not specified
CNA Linux Linux affected bae19fdd7e9e759580ac4693d2df3bc23ab415d7 07c60dda9c059c09f83d42a3ebda2e7cc1cf3bc2 git Not specified
CNA Linux Linux affected 5.19 Not specified
CNA Linux Linux unaffected 5.19 semver Not specified
CNA Linux Linux unaffected 6.12.97 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/07c60dda9c059c09f83d42a3ebda2e7cc1cf3bc2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/46d0fd8535edce31f15e48d2de1bdee39a4850e5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e9b1a7411a667539c2f55e720bbb5f623b526a32 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7cc438c99bba324a0562b1bafa747b10f7e251df 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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