Commit 71321eb3 authored by Takashi Iwai's avatar Takashi Iwai

ALSA: timer: Reject user params with too small ticks

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 126cfa2f
...@@ -1702,9 +1702,21 @@ static int snd_timer_user_params(struct file *file, ...@@ -1702,9 +1702,21 @@ static int snd_timer_user_params(struct file *file,
return -EBADFD; return -EBADFD;
if (copy_from_user(&params, _params, sizeof(params))) if (copy_from_user(&params, _params, sizeof(params)))
return -EFAULT; return -EFAULT;
if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE) && params.ticks < 1) { if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE)) {
err = -EINVAL; u64 resolution;
goto _end;
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 && if (params.queue_size > 0 &&
(params.queue_size < 32 || params.queue_size > 1024)) { (params.queue_size < 32 || params.queue_size > 1024)) {
......
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