This is a note to let you know that I've just added the patch titled
locking/rtmutex: Avoid a NULL pointer dereference on deadlock
to the 3.19-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:
locking-rtmutex-avoid-a-null-pointer-dereference-on-deadlock.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 8d1e5a1a1ccf5ae9d8a5a0ee7960202ccb0c5429 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <[email protected]>
Date: Tue, 17 Feb 2015 16:43:43 +0100
Subject: locking/rtmutex: Avoid a NULL pointer dereference on deadlock
From: Sebastian Andrzej Siewior <[email protected]>
commit 8d1e5a1a1ccf5ae9d8a5a0ee7960202ccb0c5429 upstream.
With task_blocks_on_rt_mutex() returning early -EDEADLK we never
add the waiter to the waitqueue. Later, we try to remove it via
remove_waiter() and go boom in rt_mutex_top_waiter() because
rb_entry() gives a NULL pointer.
( Tested on v3.18-RT where rtmutex is used for regular mutex and I
tried to get one twice in a row. )
Not sure when this started but I guess 397335f004f4 ("rtmutex: Fix
deadlock detector for real") or commit 3d5c9340d194 ("rtmutex:
Handle deadlock detection smarter").
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/locking/rtmutex.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1193,7 +1193,8 @@ rt_mutex_slowlock(struct rt_mutex *lock,
set_current_state(TASK_RUNNING);
if (unlikely(ret)) {
- remove_waiter(lock, &waiter);
+ if (rt_mutex_has_waiters(lock))
+ remove_waiter(lock, &waiter);
rt_mutex_handle_deadlock(ret, chwalk, &waiter);
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.19/serial-8250-revert-tty-serial-8250_core-read-only-rx-if-there-is-something-in-the-fifo.patch
queue-3.19/locking-rtmutex-avoid-a-null-pointer-dereference-on-deadlock.patch
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