CVE-2025-40327

/// Technical description

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

perf/core: Fix system hang caused by cpu-clock usage

cpu-clock usage by the async-profiler tool can trigger a system hang,

which got bisected back to the following commit by Octavia Togami:

18dbcbfabfff ("perf: Fix the POLL_HUP delivery breakage") causes this issue

The root cause of the hang is that cpu-clock is a special type of SW

event which relies on hrtimers. The __perf_event_overflow() callback

is invoked from the hrtimer handler for cpu-clock events, and

__perf_event_overflow() tries to call cpu_clock_event_stop()

to stop the event, which calls htimer_cancel() to cancel the hrtimer.

But that's a recursion into the hrtimer code from a hrtimer handler,

which (unsurprisingly) deadlocks.

To fix this bug, use hrtimer_try_to_cancel() instead, and set

the PERF_HES_STOPPED flag, which causes perf_swevent_hrtimer()

to stop the event once it sees the PERF_HES_STOPPED flag.

[ mingo: Fixed the comments and improved

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References