Commit d02479bd authored Aug 22, 2007 by Oleg Nesterov Committed by Linus Torvalds Aug 22, 2007

posix-timers: fix creation race



sys_timer_create() sets ->it_process and unlocks ->siglock, then checks
tmr->it_sigev_notify to define if get_task_struct() is needed.

We already passed ->it_id to the caller, another thread can delete this timer
and free its memory in between.

As a minimal fix, move this code under ->siglock, sys_timer_delete() takes it
too before calling release_posix_timer().  A proper serialization would be to
take ->it_lock, we add a partly initialized timer on posix_timers_id, not
good.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 179394af

kernel/posix-timers.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -547,9 +547,9 @@ sys_timer_create(const clockid_t which_clock,
		new_timer->it_process = process;
		list_add(&new_timer->list,
		&process->signal->posix_timers);
		spin_unlock_irqrestore(&process->sighand->siglock, flags);
		if (new_timer->it_sigev_notify == (SIGEV_SIGNAL\|SIGEV_THREAD_ID))
		get_task_struct(process);
		spin_unlock_irqrestore(&process->sighand->siglock, flags);
		} else {
		spin_unlock_irqrestore(&process->sighand->siglock, flags);
		process = NULL;

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