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authorTakashi Iwai <tiwai@suse.de>2017-03-24 17:07:57 +0100
committerTakashi Iwai <tiwai@suse.de>2017-03-24 17:11:00 +0100
commit2d7d54002e396c180db0c800c1046f0a3c471597 (patch)
tree69d989dd2752c6a076e74d3d2431aaf2129ebe53
parent3f307834e695f59dac4337a40316bdecfb9d0508 (diff)
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ALSA: seq: Fix race during FIFO resize
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 <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/core/seq/seq_fifo.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c
index 33980d1..01c4cfe 100644
--- 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_fifo *f, int poolsize)
/* 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;
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