CVE-2026-80602

Summary

In the Linux kernel, the following vulnerability has been resolved:

perf/x86/amd/lbr: 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_AMD_LBR_V2, perf can still report SYSRET/ERET entries for which the branch-from addresses are in the kernel.

E.g.

$ perf record -e cycles -o - -j any,save_type,u –
perf bench syscall basic –loop 1000 |
perf script -i - -F brstack|tr ' ' '\n'|
grep -E '0x[89a-f][0-9a-f]{15}'

… 0xffffffff81001268/0x717a90a38f1a/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a39157/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a2c628/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a41b60/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a260db/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a260db/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a8bef1c30/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a8e4d3c90/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH …

The reason is that the hardware filter only considers the privilege level applicable to the branch target. Extend software filtering to also validate the branch-from addresses against br_sel, so that any branch record whose branch-from address is in the kernel is dropped when PERF_SAMPLE_BRANCH_USER is requested.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/5be478c1e08981ca91b34de310d7e2638171d9d8
• https://git.kernel.org/stable/c/208ecca408b1707ad86ea247d3d3e09d3606fc13
• https://git.kernel.org/stable/c/5ab0eba9c8819506bcb72348fd701f8a9006f95e
• https://git.kernel.org/stable/c/fb3b76b5ad2ebad63dd76f8b65b624eaf638b73f
• https://git.kernel.org/stable/c/2a892294b83f541115c94b0bb637f39bef187657

• ←Previous
• Next→