ALSA: timer: Reject user params with too small ticks (71321eb3) · Commits · 戴 / test

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:

Dmitry Vyukov <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by:

Takashi Iwai <tiwai@suse.de>

sound/core/timer.c

+15 −3

Original line number	Diff line number	Diff line
		@@ -1702,10 +1702,22 @@ 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) {
		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)) {
		err = -EINVAL;

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