diff options
| author | Takashi Iwai <tiwai@suse.de> | 2016-01-30 23:09:08 +0100 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2016-03-12 14:25:46 +0100 |
| commit | 7512b9a9cfc68f4cefea8993d00edbfaf19d7948 (patch) | |
| tree | e8c71e27852480f5a3e08b1b05107aded14e61b7 | |
| parent | 774e8ca7e62f2aba6e0cc4c93538f89402ee3699 (diff) | |
| download | for-greg-7512b9a9cfc68f4cefea8993d00edbfaf19d7948.tar.gz | |
ALSA: timer: Fix link corruption due to double start or stop
commit f784beb75ce82f4136f8a0960d3ee872f7109e09 upstream.
Although ALSA timer code got hardening for races, it still causes
use-after-free error. This is however rather a corrupted linked list,
not actually the concurrent accesses. Namely, when timer start is
triggered twice, list_add_tail() is called twice, too. This ends
up with the link corruption and triggers KASAN error.
The simplest fix would be replacing list_add_tail() with
list_move_tail(), but fundamentally it's the problem that we don't
check the double start/stop correctly. So, the right fix here is to
add the proper checks to snd_timer_start() and snd_timer_stop() (and
their variants).
BugLink: http://lkml.kernel.org/r/CACT4Y+ZyPRoMQjmawbvmCEDrkBD2BQuH7R09=eOkf5ESK8kJAw@mail.gmail.com
Reported-by: Dmitry Vyukov <dvyukov@google.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>
Signed-off-by: Willy Tarreau <w@1wt.eu>
| -rw-r--r-- | sound/core/timer.c | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index ae4742d18eb17a..21f5df6734dd5a 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -439,6 +439,10 @@ static int snd_timer_start_slave(struct snd_timer_instance *timeri) unsigned long flags; spin_lock_irqsave(&slave_active_lock, flags); + if (timeri->flags & SNDRV_TIMER_IFLG_RUNNING) { + spin_unlock_irqrestore(&slave_active_lock, flags); + return -EBUSY; + } timeri->flags |= SNDRV_TIMER_IFLG_RUNNING; if (timeri->master && timeri->timer) { spin_lock(&timeri->timer->lock); @@ -463,18 +467,26 @@ int snd_timer_start(struct snd_timer_instance *timeri, unsigned int ticks) return -EINVAL; if (timeri->flags & SNDRV_TIMER_IFLG_SLAVE) { result = snd_timer_start_slave(timeri); - snd_timer_notify1(timeri, SNDRV_TIMER_EVENT_START); + if (result >= 0) + snd_timer_notify1(timeri, SNDRV_TIMER_EVENT_START); return result; } timer = timeri->timer; if (timer == NULL) return -EINVAL; spin_lock_irqsave(&timer->lock, flags); + if (timeri->flags & (SNDRV_TIMER_IFLG_RUNNING | + SNDRV_TIMER_IFLG_START)) { + result = -EBUSY; + goto unlock; + } timeri->ticks = timeri->cticks = ticks; timeri->pticks = 0; result = snd_timer_start1(timer, timeri, ticks); + unlock: spin_unlock_irqrestore(&timer->lock, flags); - snd_timer_notify1(timeri, SNDRV_TIMER_EVENT_START); + if (result >= 0) + snd_timer_notify1(timeri, SNDRV_TIMER_EVENT_START); return result; } @@ -490,6 +502,10 @@ static int _snd_timer_stop(struct snd_timer_instance * timeri, if (timeri->flags & SNDRV_TIMER_IFLG_SLAVE) { if (!keep_flag) { spin_lock_irqsave(&slave_active_lock, flags); + if (!(timeri->flags & SNDRV_TIMER_IFLG_RUNNING)) { + spin_unlock_irqrestore(&slave_active_lock, flags); + return -EBUSY; + } timeri->flags &= ~SNDRV_TIMER_IFLG_RUNNING; list_del_init(&timeri->ack_list); list_del_init(&timeri->active_list); @@ -501,6 +517,11 @@ static int _snd_timer_stop(struct snd_timer_instance * timeri, if (!timer) return -EINVAL; spin_lock_irqsave(&timer->lock, flags); + if (!(timeri->flags & (SNDRV_TIMER_IFLG_RUNNING | + SNDRV_TIMER_IFLG_START))) { + spin_unlock_irqrestore(&timer->lock, flags); + return -EBUSY; + } list_del_init(&timeri->ack_list); list_del_init(&timeri->active_list); if ((timeri->flags & SNDRV_TIMER_IFLG_RUNNING) && @@ -566,10 +587,15 @@ int snd_timer_continue(struct snd_timer_instance *timeri) if (! timer) return -EINVAL; spin_lock_irqsave(&timer->lock, flags); + if (timeri->flags & SNDRV_TIMER_IFLG_RUNNING) { + result = -EBUSY; + goto unlock; + } if (!timeri->cticks) timeri->cticks = 1; timeri->pticks = 0; result = snd_timer_start1(timer, timeri, timer->sticks); + unlock: spin_unlock_irqrestore(&timer->lock, flags); snd_timer_notify1(timeri, SNDRV_TIMER_EVENT_CONTINUE); return result; |