Bug 2420242 (CVE-2023-53815)

Summary: CVE-2023-53815 kernel: posix-timers: Prevent RT livelock in itimer_delete()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-12-09 01:02:44 UTC 
In the Linux kernel, the following vulnerability has been resolved:

posix-timers: Prevent RT livelock in itimer_delete()

itimer_delete() has a retry loop when the timer is concurrently expired. On
non-RT kernels this just spin-waits until the timer callback has completed,
except for posix CPU timers which have HAVE_POSIX_CPU_TIMERS_TASK_WORK
enabled.

In that case and on RT kernels the existing task could live lock when
preempting the task which does the timer delivery.

Replace spin_unlock() with an invocation of timer_wait_running() to handle
it the same way as the other retry loops in the posix timer code.
Comment 1 Alexander B 2025-12-10 07:55:28 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120945-CVE-2023-53815-5695@gregkh/T