Commit f99588fa authored by Takashi Iwai's avatar Takashi Iwai Committed by Ben Hutchings

ALSA: timer: Reject user params with too small ticks

commit 71321eb3 upstream.

When a user sets a too small ticks with a fine-grained timer like
hrtimer, the kernel tries to fire up the timer irq too frequently.
This may lead to the condensed locks, eventually the kernel spinlock
lockup with warnings.

For avoiding such a situation, we define a lower limit of the
resolution, namely 1ms.  When the user passes a too small tick value
that results in less than that, the kernel returns -EINVAL now.
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 812c9cd9
......@@ -1715,9 +1715,21 @@ static int snd_timer_user_params(struct file *file,
return -EBADFD;
if (copy_from_user(&params, _params, sizeof(params)))
return -EFAULT;
if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE) && params.ticks < 1) {
err = -EINVAL;
goto _end;
if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE)) {
u64 resolution;
if (params.ticks < 1) {
err = -EINVAL;
goto _end;
}
/* Don't allow resolution less than 1ms */
resolution = snd_timer_resolution(tu->timeri);
resolution *= params.ticks;
if (resolution < 1000000) {
err = -EINVAL;
goto _end;
}
}
if (params.queue_size > 0 &&
(params.queue_size < 32 || params.queue_size > 1024)) {
......
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