This is a note to let you know that I've just added the patch titled
ipc/sem.c: fix race with concurrent semtimedop() timeouts
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipc-sem.c-fix-race-with-concurrent-semtimedop-timeouts.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From d694ad62bf539dbb20a0899ac2a954555f9e4a83 Mon Sep 17 00:00:00 2001
From: Manfred Spraul <[email protected]>
Date: Mon, 25 Jul 2011 17:11:47 -0700
Subject: ipc/sem.c: fix race with concurrent semtimedop() timeouts
and IPC_RMID
From: Manfred Spraul <[email protected]>
commit d694ad62bf539dbb20a0899ac2a954555f9e4a83 upstream.
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 <[email protected]>
Reported-by: Harald Laabs <[email protected]>
Signed-off-by: Manfred Spraul <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
ipc/sem.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1456,15 +1456,24 @@ SYSCALL_DEFINE4(semtimedop, int, 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)) {
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) {
Patches currently in stable-queue which might be from [email protected]
are
queue-3.0/ipc-sem.c-fix-race-with-concurrent-semtimedop-timeouts.patch
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