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| author | Manfred Spraul <manfred@colorfullife.com> | 2011-07-25 17:11:47 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-25 20:57:07 -0700 |
| commit | d694ad62bf539dbb20a0899ac2a954555f9e4a83 (patch) | |
| tree | fd3ddc3269b6ad40a448046e60560fec30fbb0c5 /ipc/sem.c | |
| parent | 8405b044e5238afebd7248d927c1d261d2239767 (diff) | |
| download | lwn-d694ad62bf539dbb20a0899ac2a954555f9e4a83.tar.gz lwn-d694ad62bf539dbb20a0899ac2a954555f9e4a83.zip | |
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=27142
Reported-by: Yuriy Yevtukhov <yuriy@ucoz.com>
Reported-by: Harald Laabs <kernel@dasr.de>
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: <stable@kernel.org> [2.6.35+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index 8b929e6a6eda..c8e00f8b4be1 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1450,15 +1450,24 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, } 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)) { error = -EIDRM; 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) { |