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| author | Takashi Iwai <tiwai@suse.de> | 2016-02-09 12:02:32 +0100 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2016-02-15 17:07:54 +0100 |
| commit | aa482b4ddf287095641a49f0343aff8f161c67c2 (patch) | |
| tree | e96a8c08327781e31ed7cfdddf632e69b23a7a7b /sound | |
| parent | 009e4dbe919bfd67f9ce7800885a34008d730982 (diff) | |
| download | lwn-aa482b4ddf287095641a49f0343aff8f161c67c2.tar.gz lwn-aa482b4ddf287095641a49f0343aff8f161c67c2.zip | |
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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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 ef62ffbcfa8c..d90d8f4b85fe 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -508,9 +508,13 @@ static int _snd_timer_stop(struct snd_timer_instance *timeri, int event) 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; } |