[PATCH 3/3] posix timers: release_posix_timer: kill the bogus put_task_struct(->it_process);

From: Oleg Nesterov
Date: Sat May 17 2008 - 11:14:46 EST

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 <oleg@xxxxxxxxxx>
Acked-by: Roland McGrath <roland@xxxxxxxxxx>

--- 25/kernel/posix-timers.c~3_RPT_NO_CHECK 2008-05-17 16:31:26.000000000 +0400
+++ 25/kernel/posix-timers.c 2008-05-17 16:38:07.000000000 +0400
@@ -450,9 +450,6 @@ static void release_posix_timer(struct k
spin_unlock_irqrestore(&idr_lock, flags);
- 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);

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