CVE-2026-97960perf/x86/intel: Prevent drain_pebs() reentry

Official description

In the Linux kernel, the following vulnerability has been resolved: perf/x86/intel: Prevent drain_pebs() reentry The PEBS buffer is shared by all events on a CPU, so drain_pebs() must not be reentered. If so, one instance may observe stale buffer state and potentially access out-of-bound memory. Most invocations happen in NMI context, which naturally prevents reentry. However, drain_pebs() is also reachable from process context via intel_pmu_drain_pebs_buffer(). In those paths, the PMU is often already disabled, but not guaranteed. For example, __intel_pmu_pebs_disable() only disables the target counter, so other active counters can still raise a PMI and interrupt an in-flight drain_pebs(). Here is an example, __perf_addr_filters_adjust() perf_event_stop() __perf_event_stop() x86_pmu_stop() (event->pmu->stop) intel_pmu_disable_event() intel_pmu_pebs_disable() __intel_pmu_pebs_disable() intel_pmu_drain_large_pebs() intel_pmu_drain_pebs_buffer() Introduce __intel_pmu_quiesce() and __intel_pmu_resume() helpers and use them in intel_pmu_drain_large_pebs() to disable the full PMU around the intel_pmu_drain_pebs_buffer() call, preventing reentry. Also add a warning in intel_pmu_drain_pebs_buffer() when the full PMU is not disabled.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/9882068ed242fcd4743f53027e8c790e88dcafff
• https://git.kernel.org/stable/c/999e482fdf89400cc1ae937680fc05096b4c915b
• https://git.kernel.org/stable/c/a5fe19dd8b3ed5fad6e5e0f0c58c7245043ee4af
• https://git.kernel.org/stable/c/c55599c0ec2aa020e41a0599c3044c56d8a2e7d9
• https://git.kernel.org/stable/c/a56c03a397e2cd0c4cf8da96dcd6214f7d0e7d8c