CVE-2026-72237perf/x86/amd/brs: Fix kernel address leakage

Official description

In the Linux kernel, the following vulnerability has been resolved: perf/x86/amd/brs: Fix kernel address leakage A user-only branch stack can contain branches that originate from the kernel. As a result, kernel addresses are exposed to user space even when PERF_SAMPLE_BRANCH_USER is requested. On AMD processors supporting X86_FEATURE_BRS (Zen 3 only), perf can still report entries such as SYSRET/interrupt returns for which the branch-from addresses are in the kernel. E.g. $ perf record -j any,u -c 4000 -e branch-brs -o - -- \ perf bench syscall basic --loop 1000 | \ perf script -i - -F brstack|tr ' ' '\n'| \ grep -E '0x[89a-f][0-9a-f]{15}' ... 0xffffffff810001c4/0x72e2e32955eb/-/-/-/0//- 0xffffffff810001c4/0x72e2d94a9821/-/-/-/0//- 0xffffffff810001c4/0x72e2d94ffa1b/-/-/-/0//- ... BRS provides no hardware branch filtering, so privilege level filtering is performed entirely in software. However, amd_brs_match_plm() only validates the branch-to address against the requested privilege levels. For branches from the kernel to user space, the branch-from address is left unchecked and is leaked. Extend the software filter to also validate the branch-from address, so that any branch record whose branch-from address is in the kernel is dropped when PERF_SAMPLE_BRANCH_USER is requested.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4f949bc3913a6e3ce3b8574ac6ed1da8ec7a5ad1
• https://git.kernel.org/stable/c/ac44b4a3d6137489f8fa2e794b12e849c6b22eaa
• https://git.kernel.org/stable/c/90843d00dbc61220b66408ea0d8775cae9e51f70
• https://git.kernel.org/stable/c/046f6244da9b68e463a849b21446b9424e531491
• https://git.kernel.org/stable/c/2e706be56f418718bb3ae66c0aa94f9b61150e6d
• https://git.kernel.org/stable/c/47915e855fb38b42133e31ba917d99565f862154