tree 3b76d3b132721e80eac0cd86701283579de5a688
parent 344c9ac65ea678fafaff5074361dead24a038c27
author Takashi Iwai <tiwai@suse.de> 1518445251 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1519310631 +0100

ALSA: seq: Fix racy pool initializations

commit d15d662e89fc667b90cd294b0eb45694e33144da upstream.

ALSA sequencer core initializes the event pool on demand by invoking
snd_seq_pool_init() when the first write happens and the pool is
empty.  Meanwhile user can reset the pool size manually via ioctl
concurrently, and this may lead to UAF or out-of-bound accesses since
the function tries to vmalloc / vfree the buffer.

A simple fix is to just wrap the snd_seq_pool_init() call with the
recently introduced client->ioctl_mutex; as the calls for
snd_seq_pool_init() from other side are always protected with this
mutex, we can avoid the race.

Reported-by: 范龙飞 <long7573@126.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>