diff options
| author | Takashi Iwai <tiwai@suse.de> | 2016-02-09 12:02:32 +0100 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2016-02-09 12:02:32 +0100 |
| commit | ed8b1d6d2c741ab26d60d499d7fbb7ac801f0f51 (patch) | |
| tree | 1321d353d8fc88fa201ec6f27dfa7d32468e0b0d /sound | |
| parent | 117159f0b9d392fb433a7871426fad50317f06f7 (diff) | |
| download | lwn-ed8b1d6d2c741ab26d60d499d7fbb7ac801f0f51.tar.gz lwn-ed8b1d6d2c741ab26d60d499d7fbb7ac801f0f51.zip | |
ALSA: timer: Fix race between stop and interrupt
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
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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 dea932ac6165..a0405b0078c6 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -518,9 +518,13 @@ 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; } |