diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2015-02-17 16:18:05 +0100 |
|---|---|---|
| committer | Anders Roxell <anders.roxell@linaro.org> | 2015-06-26 22:31:38 +0200 |
| commit | 6e2a00525a3267c0afc87fc9506686ef26c06055 (patch) | |
| tree | b1c55cfd01df189fa3f1241c357970c019b4c3c0 | |
| parent | c2ff10c0ac1d5ad417fd9e9e9caebdd08428c62e (diff) | |
locking/rt-mutex: 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 397335f00 ("rtmutex: Fix deadlock
detector for real") or commit 3d5c9340 ("rtmutex: Handle deadlock
detection smarter").
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
| -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 a0d9eadcfe02..ec72272ab73a 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1697,7 +1697,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, 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); } else if (ww_ctx) { ww_mutex_account_lock(lock, ww_ctx); |