From df7a2d0af9f7ab73cf22a7b62bbc0bad93a02110 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 24 Mar 2017 17:07:57 +0100 Subject: [PATCH] ALSA: seq: Fix race during FIFO resize 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(+) diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c index fc2c55b18f49e..490b697e83ff5 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; -- 2.47.2