Commit d694ad62 authored by Manfred Spraul's avatar Manfred Spraul Committed by Linus Torvalds

ipc/sem.c: fix race with concurrent semtimedop() timeouts and IPC_RMID

If a semaphore array is removed and in parallel a sleeping task is woken
up (signal or timeout, does not matter), then the woken up task does not
wait until wake_up_sem_queue_do() is completed.  This will cause crashes,
because wake_up_sem_queue_do() will read from a stale pointer.

The fix is simple: Regardless of anything, always call get_queue_result().
This function waits until wake_up_sem_queue_do() has finished it's task.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=27142Reported-by: default avatarYuriy Yevtukhov <yuriy@ucoz.com>
Reported-by: default avatarHarald Laabs <kernel@dasr.de>
Signed-off-by: default avatarManfred Spraul <manfred@colorfullife.com>
Acked-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: <stable@kernel.org>		[2.6.35+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8405b044
...@@ -1450,15 +1450,24 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, ...@@ -1450,15 +1450,24 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
} }
sma = sem_lock(ns, semid); sma = sem_lock(ns, semid);
/*
* Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
*/
error = get_queue_result(&queue);
/*
* Array removed? If yes, leave without sem_unlock().
*/
if (IS_ERR(sma)) { if (IS_ERR(sma)) {
error = -EIDRM; error = -EIDRM;
goto out_free; goto out_free;
} }
error = get_queue_result(&queue);
/* /*
* If queue.status != -EINTR we are woken up by another process * If queue.status != -EINTR we are woken up by another process.
* Leave without unlink_queue(), but with sem_unlock().
*/ */
if (error != -EINTR) { if (error != -EINTR) {
......
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