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authorTakashi Iwai <tiwai@suse.de>2018-05-16 23:52:42 +0200
committerTakashi Iwai <tiwai@suse.de>2018-05-18 08:49:13 +0200
commit9d4d207d1346329c5295420254f1dbef1a6ab6ba (patch)
tree5fcb084352753cfd57e434768cbdb1f774257030 /sound/core/timer.c
parent21244e3d6a9d36f32a2aa40f8948324c7b5f35b0 (diff)
downloadlinux-9d4d207d1346329c5295420254f1dbef1a6ab6ba.tar.bz2
ALSA: timer: Assure timer resolution access always locked
There are still many places calling the timer's hw.c_resolution callback without lock, and this may lead to some races, as we faced in the commit a820ccbe21e8 ("ALSA: pcm: Fix UAF at PCM release via PCM timer access"). This patch changes snd_timer_resolution() to take the timer->lock for avoiding the races. A place calling this function already inside the lock (from the notifier) is replaced with the snd_timer_hw_resolution() accordingly, as well as wrapping with the lock around another place calling snd_timer_hw_resolution(), too. Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/timer.c')
-rw-r--r--sound/core/timer.c23
1 files changed, 15 insertions, 8 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c
index 22c72857f379..665089c45560 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -438,19 +438,24 @@ static unsigned long snd_timer_hw_resolution(struct snd_timer *timer)
unsigned long snd_timer_resolution(struct snd_timer_instance *timeri)
{
struct snd_timer * timer;
+ unsigned long ret = 0;
+ unsigned long flags;
if (timeri == NULL)
return 0;
timer = timeri->timer;
- if (timer)
- return snd_timer_hw_resolution(timer);
- return 0;
+ if (timer) {
+ spin_lock_irqsave(&timer->lock, flags);
+ ret = snd_timer_hw_resolution(timer);
+ spin_unlock_irqrestore(&timer->lock, flags);
+ }
+ return ret;
}
EXPORT_SYMBOL(snd_timer_resolution);
static void snd_timer_notify1(struct snd_timer_instance *ti, int event)
{
- struct snd_timer *timer;
+ struct snd_timer *timer = ti->timer;
unsigned long resolution = 0;
struct snd_timer_instance *ts;
struct timespec tstamp;
@@ -462,14 +467,14 @@ static void snd_timer_notify1(struct snd_timer_instance *ti, int event)
if (snd_BUG_ON(event < SNDRV_TIMER_EVENT_START ||
event > SNDRV_TIMER_EVENT_PAUSE))
return;
- if (event == SNDRV_TIMER_EVENT_START ||
- event == SNDRV_TIMER_EVENT_CONTINUE)
- resolution = snd_timer_resolution(ti);
+ if (timer &&
+ (event == SNDRV_TIMER_EVENT_START ||
+ event == SNDRV_TIMER_EVENT_CONTINUE))
+ resolution = snd_timer_hw_resolution(timer);
if (ti->ccallback)
ti->ccallback(ti, event, &tstamp, resolution);
if (ti->flags & SNDRV_TIMER_IFLG_SLAVE)
return;
- timer = ti->timer;
if (timer == NULL)
return;
if (timer->hw.flags & SNDRV_TIMER_HW_SLAVE)
@@ -1654,6 +1659,7 @@ static int snd_timer_user_gstatus(struct file *file,
mutex_lock(&register_mutex);
t = snd_timer_find(&tid);
if (t != NULL) {
+ spin_lock_irq(&t->lock);
gstatus.resolution = snd_timer_hw_resolution(t);
if (t->hw.precise_resolution) {
t->hw.precise_resolution(t, &gstatus.resolution_num,
@@ -1662,6 +1668,7 @@ static int snd_timer_user_gstatus(struct file *file,
gstatus.resolution_num = gstatus.resolution;
gstatus.resolution_den = 1000000000uL;
}
+ spin_unlock_irq(&t->lock);
} else {
err = -ENODEV;
}