Patch "ALSA: timer: Reject user params with too small ticks" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: timer: Reject user params with too small ticks

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-timer-reject-user-params-with-too-small-ticks.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Tue, 28 Feb 2017 14:49:07 +0100
Subject: ALSA: timer: Reject user params with too small ticks

From: Takashi Iwai <[email protected]>

commit 71321eb3f2d0df4e6c327e0b936eec4458a12054 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.

---
 sound/core/timer.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

@@ -1700,9 +1700,21 @@ static int snd_timer_user_params(struct
 		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)) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/alsa-hda-add-subwoofer-support-for-dell-inspiron-17-7000-gaming.patch queue-4.4/alsa-seq-fix-link-corruption-by-event-error-handling.patch queue-4.4/alsa-hda-fix-micmute-hotkey-problem-for-a-lenovo-aio-machine.patch queue-4.4/alsa-ctxfi-fallback-dma-mask-to-32bit.patch queue-4.4/alsa-timer-reject-user-params-with-too-small-ticks.patch queue-4.4/alsa-hda-fix-lewisburg-audio-issue.patch queue-4.4/alsa-hda-realtek-cannot-adjust-speaker-s-volume-on-a-dell-aio.patch