[lkml]   [2017]   [Jul]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 3.2 45/95] ALSA: seq: Fix race during FIFO resize
3.2.91-rc1 review patch.  If anyone has any objections, please let me know.


From: Takashi Iwai <>

commit 2d7d54002e396c180db0c800c1046f0a3c471597 upstream.

When a new event is queued while processing to resize the FIFO in
snd_seq_fifo_clear(), it may lead to a use-after-free, as the old pool
that is being queued gets removed. For avoiding this race, we need to
close the pool to be deleted and sync its usage before actually
deleting it.

The issue was spotted by syzkaller.

Reported-by: Dmitry Vyukov <>
Signed-off-by: Takashi Iwai <>
Signed-off-by: Ben Hutchings <>
sound/core/seq/seq_fifo.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/sound/core/seq/seq_fifo.c
+++ b/sound/core/seq/seq_fifo.c
@@ -267,6 +267,10 @@ int snd_seq_fifo_resize(struct snd_seq_f
/* NOTE: overflow flag is not cleared */
spin_unlock_irqrestore(&f->lock, flags);

+ /* close the old pool and wait until all users are gone */
+ snd_seq_pool_mark_closing(oldpool);
+ snd_use_lock_sync(&f->use_lock);
/* release cells in old pool */
for (cell = oldhead; cell; cell = next) {
next = cell->next;
 \ /
  Last update: 2017-07-16 16:51    [W:0.228 / U:2.260 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site