From c36ef6467420f8982e6d4d6f93d0634a85a5ee45 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: Greg Kroah-Hartman --- 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 3f4efcb85df55..3490d21ab9e7f 100644 --- a/sound/core/seq/seq_fifo.c +++ b/sound/core/seq/seq_fifo.c @@ -265,6 +265,10 @@ 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; -- 2.47.3