diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2015-02-17 16:43:43 +0100 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2015-03-02 15:04:30 +0000 |
| commit | eb9abcff096d2b1d89cbf9d968714c339b6f94c3 (patch) | |
| tree | a5cef49b7112dcfa4686efdb332dfd8f2a8486a9 /kernel/locking | |
| parent | dae27fb6ff12f3fb1599343ebc0372db324b2ad3 (diff) | |
locking/rtmutex: Avoid a NULL pointer dereference on deadlock
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 <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1424187823-19600-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Diffstat (limited to 'kernel/locking')
| -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 fc605941b9b8..f9878d16b80b 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -936,7 +936,8 @@ 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, detect_deadlock, &waiter); } |