Patch "ALSA: seq: Don't handle loop timeout at snd_seq_pool_done()" 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: seq: Don't handle loop timeout at snd_seq_pool_done()

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-seq-don-t-handle-loop-timeout-at-snd_seq_pool_done.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: Mon, 6 Feb 2017 15:09:48 +0100
Subject: ALSA: seq: Don't handle loop timeout at snd_seq_pool_done()

From: Takashi Iwai <[email protected]>

commit 37a7ea4a9b81f6a864c10a7cb0b96458df5310a3 upstream.

snd_seq_pool_done() syncs with closing of all opened threads, but it aborts the wait loop with a timeout, and proceeds to the release resource even if not all threads have been closed. The timeout was 5 seconds, and if you run a crazy stuff, it can exceed easily, and may result in the access of the invalid memory address -- this is what syzkaller detected in a bug report.

As a fix, let the code graduate from naiveness, simply remove the loop timeout.

---
 sound/core/seq/seq_memory.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

@@ -419,7 +419,6 @@ int snd_seq_pool_done(struct snd_seq_poo
 {
 	unsigned long flags;
 	struct snd_seq_event_cell *ptr;
-	int max_count = 5 * HZ;
 
 	if (snd_BUG_ON(!pool))
 		return -EINVAL;

@@ -432,14 +431,8 @@ int snd_seq_pool_done(struct snd_seq_poo
 	if (waitqueue_active(&pool->output_sleep))
 		wake_up(&pool->output_sleep);
 
-	while (atomic_read(&pool->counter) > 0) {
-		if (max_count == 0) {
-			pr_warn("ALSA: snd_seq_pool_done timeout: %d cells remain\n", atomic_read(&pool->counter));
-			break;
-		}
+	while (atomic_read(&pool->counter) > 0)
 		schedule_timeout_uninterruptible(1);
-		max_count--;
-	}
 	
 	/* release all resources */
 	spin_lock_irqsave(&pool->lock, flags);

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

queue-4.4/alsa-seq-don-t-handle-loop-timeout-at-snd_seq_pool_done.patch queue-4.4/alsa-seq-fix-race-at-creating-a-queue.patch