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authorTakashi Iwai <tiwai@suse.de>2016-02-09 12:02:32 +0100
committerTakashi Iwai <tiwai@suse.de>2016-02-09 12:02:32 +0100
commited8b1d6d2c741ab26d60d499d7fbb7ac801f0f51 (patch)
tree1321d353d8fc88fa201ec6f27dfa7d32468e0b0d
parentALSA: timer: Fix wrong instance passed to slave callbacks (diff)
downloadlinux-ed8b1d6d2c741ab26d60d499d7fbb7ac801f0f51.tar.xz
linux-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>
-rw-r--r--sound/core/timer.c4
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;
}