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ALSA: timer: Limit max amount of slave instances

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[ Upstream commit fdea53fe5de532969a332d6e5e727f2ad8bf084d ]

The fuzzer tries to open the timer instances as much as possible, and
this may cause a system hiccup easily.  We've already introduced the
cap for the max number of available instances for the h/w timers, and
we should put such a limit also to the slave timers, too.

This patch introduces the limit to the multiple opened slave timers.
The upper limit is hard-coded to 1000 for now, which should suffice
for any practical usages up to now.

Link: https://lore.kernel.org/r/20191106154257.5853-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Takashi Iwai 2019-11-06 16:42:57 +01:00 committed by Greg Kroah-Hartman
parent b90fd09850
commit 691960eaa2
1 changed files with 10 additions and 0 deletions
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10
sound/core/timer.c
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@ -88,6 +88,9 @@ static LIST_HEAD(snd_timer_slave_list);
/* lock for slave active lists */
static DEFINE_SPINLOCK(slave_active_lock);
#define MAX_SLAVE_INSTANCES 1000
static int num_slaves;
static DEFINE_MUTEX(register_mutex);
static int snd_timer_free(struct snd_timer *timer);
@ -266,6 +269,10 @@ int snd_timer_open(struct snd_timer_instance **ti,
err = -EINVAL;
goto unlock;
}
if (num_slaves >= MAX_SLAVE_INSTANCES) {
err = -EBUSY;
goto unlock;
}
timeri = snd_timer_instance_new(owner, NULL);
if (!timeri) {
err = -ENOMEM;
@ -275,6 +282,7 @@ int snd_timer_open(struct snd_timer_instance **ti,
timeri->slave_id = tid->device;
timeri->flags |= SNDRV_TIMER_IFLG_SLAVE;
list_add_tail(&timeri->open_list, &snd_timer_slave_list);
num_slaves++;
err = snd_timer_check_slave(timeri);
if (err < 0) {
snd_timer_close_locked(timeri, &card_dev_to_put);
@ -364,6 +372,8 @@ static int snd_timer_close_locked(struct snd_timer_instance *timeri,
struct snd_timer_instance *slave, *tmp;
list_del(&timeri->open_list);
if (timeri->flags & SNDRV_TIMER_IFLG_SLAVE)
num_slaves--;
/* force to stop the timer */
snd_timer_stop(timeri);