---
id: CVE-2025-40327
title: |-
  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 com…
summary: |-
  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 com…
severity: none
published: '2025-12-09'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T19:10:00.173'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-40327'
references:
  - url: 'https://git.kernel.org/stable/c/6b8c512811644cf2f5eaf6f44e928683c54127f0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/eb3182ef0405ff2f6668fd3e5ff9883f60ce8801'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.0021
epssPercentile: 0.10444
ingestedAt: '2026-10-15T19:25:46.340Z'
---

## Overview

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 the changelog. ]

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.