From: Oleg Nesterov release_posix_timer() can't be called with ->it_process != NULL. Once sys_timer_create() sets ->it_process it must not call release_posix_timer(), otherwise we can race with another thread doing sys_timer_delete(), this timer is visible to idr_find() and unlocked. The same is true for two other callers (actually, for any possible caller), sys_timer_delete() and itimer_delete(). They must clear ->it_process before unlock_timer() + release_posix_timer(). Signed-off-by: Oleg Nesterov Acked-by: Roland McGrath Cc: john stultz Cc: Thomas Gleixner Cc: Roland McGrath Signed-off-by: Andrew Morton --- kernel/posix-timers.c | 3 --- 1 file changed, 3 deletions(-) diff -puN kernel/posix-timers.c~posix-timers-release_posix_timer-kill-the-bogus-put_task_struct-it_process kernel/posix-timers.c --- a/kernel/posix-timers.c~posix-timers-release_posix_timer-kill-the-bogus-put_task_struct-it_process +++ a/kernel/posix-timers.c @@ -449,9 +449,6 @@ static void release_posix_timer(struct k spin_unlock_irqrestore(&idr_lock, flags); } sigqueue_free(tmr->sigq); - if (unlikely(tmr->it_process) && - tmr->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID)) - put_task_struct(tmr->it_process); kmem_cache_free(posix_timers_cache, tmr); } _