UBUNTU-CVE-2025-40327
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. ]
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
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13 explicit affected versions
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45 explicit affected versions
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11 explicit affected versions
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1 explicit affected versions
13 explicit affected versions
43 explicit affected versions
6 explicit affected versions
10 explicit affected versions
8 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
6 explicit affected versions
11 explicit affected versions
1 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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. ]
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/eb3182ef0405ff2f6668fd3e5ff9883f60ce8801
- https://git.kernel.org/stable/c/6b8c512811644cf2f5eaf6f44e928683c54127f0
- https://git.kernel.org/stable/c/eb3182ef0405ff2f6668fd3e5ff9883f60ce8801
- https://ubuntu.com/security/CVE-2025-40327
- https://ubuntu.com/security/notices/USN-8029-1
- https://ubuntu.com/security/notices/USN-8029-2
- https://ubuntu.com/security/notices/USN-8029-3
- https://ubuntu.com/security/notices/USN-8030-1
- https://ubuntu.com/security/notices/USN-8048-1
- https://www.cve.org/CVERecord?id=CVE-2025-40327