CVE-2025-38352posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del()

Official description

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() If an exiting non-autoreaping task has already passed exit_notify() and calls handle_posix_cpu_timers() from IRQ, it can be reaped by its parent or debugger right after unlock_task_sighand(). If a concurrent posix_cpu_timer_del() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cpu_timer_task_rcu() and/or lock_task_sighand() will fail. Add the tsk->exit_state check into run_posix_cpu_timers() to fix this. This fix is not needed if CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, because exit_task_work() is called before exit_notify(). But the check still makes sense, task_work_add(&tsk->posix_cputimers_work.work) will fail anyway in this case.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/78a4b8e3795b31dae58762bc091bb0f4f74a2200
• https://git.kernel.org/stable/c/c076635b3a42771ace7d276de8dc3bc76ee2ba1b
• https://git.kernel.org/stable/c/2f3daa04a9328220de46f0d5c919a6c0073a9f0b
• https://git.kernel.org/stable/c/764a7a5dfda23f69919441f2eac2a83e7db6e5bb
• https://git.kernel.org/stable/c/2c72fe18cc5f9f1750f5bc148cf1c94c29e106ff
• https://git.kernel.org/stable/c/c29d5318708e67ac13c1b6fc1007d179fb65b4d7
• https://git.kernel.org/stable/c/460188bc042a3f40f72d34b9f7fc6ee66b0b757b
• https://git.kernel.org/stable/c/f90fff1e152dedf52b932240ebbd670d83330eca
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-38352 government-resource
• https://github.com/farazsth98/chronomaly exploit
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html