In the Linux kernel, the following vulnerability has been resolved:
posix-cpu-timers: fix race between handleposixcputimers() and posixcputimerdel()
If an exiting non-autoreaping task has already passed exitnotify() and calls handleposixcputimers() from IRQ, it can be reaped by its parent or debugger right after unlocktasksighand().
If a concurrent posixcputimerdel() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cputimertaskrcu() and/or locktasksighand() will fail.
Add the tsk->exitstate check into runposixcputimers() to fix this.
This fix is not needed if CONFIGPOSIXCPUTIMERSTASKWORK=y, because exittaskwork() is called before exitnotify(). But the check still makes sense, taskworkadd(&tsk->posixcputimerswork.work) will fail anyway in this case.