CVE-2026-31528perf: Make sure to use pmu_ctx->pmu for groups

Official description

In the Linux kernel, the following vulnerability has been resolved: perf: Make sure to use pmu_ctx->pmu for groups Oliver reported that x86_pmu_del() ended up doing an out-of-bound memory access when group_sched_in() fails and needs to roll back. This *should* be handled by the transaction callbacks, but he found that when the group leader is a software event, the transaction handlers of the wrong PMU are used. Despite the move_group case in perf_event_open() and group_sched_in() using pmu_ctx->pmu. Turns out, inherit uses event->pmu to clone the events, effectively undoing the move_group case for all inherited contexts. Fix this by also making inherit use pmu_ctx->pmu, ensuring all inherited counters end up in the same pmu context. Similarly, __perf_event_read() should use equally use pmu_ctx->pmu for the group case.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/656f35b463995bee024d948440128230aacd81e1
• https://git.kernel.org/stable/c/3a696e84a8b1fafdd774bb30d62919faf844d9e4
• https://git.kernel.org/stable/c/35f7914e54fe7f13654c22ee045b05e4b6d8062b
• https://git.kernel.org/stable/c/4c759446046500a1a6785b25725725c3ff087ace
• https://git.kernel.org/stable/c/4b9ce671960627b2505b3f64742544ae9801df97