diff options
| author | Takashi Iwai <tiwai@suse.de> | 2016-02-09 12:02:32 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2016-02-27 14:28:48 +0000 |
| commit | 8470405c5ed05d9b916801e54fd36acd909a4e6f (patch) | |
| tree | 9fac62aaf607ec07cd5b50b7eb25c359e2ab68bb /sound | |
| parent | 152e8fcbc0e7102a037b0dfd7551bb95e289ce16 (diff) | |
ALSA: timer: Fix race between stop and interrupt
commit ed8b1d6d2c741ab26d60d499d7fbb7ac801f0f51 upstream.
A slave timer element also unlinks at snd_timer_stop() but it takes
only slave_active_lock. When a slave is assigned to a master,
however, this may become a race against the master's interrupt
handling, eventually resulting in a list corruption. The actual bug
could be seen with a syzkaller fuzzer test case in BugLink below.
As a fix, we need to take timeri->timer->lock when timer isn't NULL,
i.e. assigned to a master, while the assignment to a master itself is
protected by slave_active_lock.
BugLink: http://lkml.kernel.org/r/CACT4Y+Y_Bm+7epAb=8Wi=AaWd+DYS7qawX52qxdCfOfY49vozQ@mail.gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'sound')
| -rw-r--r-- | sound/core/timer.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index 972a5f16b3e7..9198fe24ae93 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -510,9 +510,13 @@ static int _snd_timer_stop(struct snd_timer_instance * timeri, spin_unlock_irqrestore(&slave_active_lock, flags); return -EBUSY; } + if (timeri->timer) + spin_lock(&timeri->timer->lock); timeri->flags &= ~SNDRV_TIMER_IFLG_RUNNING; list_del_init(&timeri->ack_list); list_del_init(&timeri->active_list); + if (timeri->timer) + spin_unlock(&timeri->timer->lock); spin_unlock_irqrestore(&slave_active_lock, flags); } goto __end; |