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| author | Takashi Iwai <tiwai@suse.de> | 2016-02-09 12:02:32 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-02-17 12:34:37 -0800 |
| commit | 71f32f598bed163d9527598014abf0344157a048 (patch) | |
| tree | f92342c1785cb5efdff70414f3522b29a252f73d | |
| parent | d2bfc1530dbdc75b3b06afa8b09479d2f5d36252 (diff) | |
| download | lwn-71f32f598bed163d9527598014abf0344157a048.tar.gz lwn-71f32f598bed163d9527598014abf0344157a048.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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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; } |