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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2015-02-17 16:43:43 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-02-18 10:20:32 +0100 |
| commit | 8d1e5a1a1ccf5ae9d8a5a0ee7960202ccb0c5429 (patch) | |
| tree | 6aac63d8cc0d62875f96fc2120afa3b8a5baff88 /kernel | |
| parent | e07e0d4cb0c4bfe822ec8491cc06269096a38bea (diff) | |
| download | lwn-8d1e5a1a1ccf5ae9d8a5a0ee7960202ccb0c5429.tar.gz lwn-8d1e5a1a1ccf5ae9d8a5a0ee7960202ccb0c5429.zip | |
locking/rtmutex: Avoid a NULL pointer dereference on deadlock
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 <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org> # for v3.16 and later kernels
Link: http://lkml.kernel.org/r/1424187823-19600-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/rtmutex.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 3059bc2f022d..e16e5542bf13 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1193,7 +1193,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); if (unlikely(ret)) { - remove_waiter(lock, &waiter); + if (rt_mutex_has_waiters(lock)) + remove_waiter(lock, &waiter); rt_mutex_handle_deadlock(ret, chwalk, &waiter); } |