3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
commit d85739367c6d56e475c281945c68fdb05ca74b4c upstream.
This is a fix for a (sort of) fallout in the recent commit d15d662e89fc ("ALSA: seq: Fix racy pool initializations") for CVE-2018-1000004. As the pool resize deletes the existing cells, it may lead to a race when another thread is writing concurrently, eventually resulting a UAF.
A simple workaround is not to allow the pool resizing when the pool is in use. It's an invalid behavior in anyway.
Fixes: d15d662e89fc ("ALSA: seq: Fix racy pool initializations") Reported-by: 范龙飞 long7573@126.com Reported-by: Nicolai Stange nstange@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Ben Hutchings ben@decadent.org.uk --- sound/core/seq/seq_clientmgr.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1929,6 +1929,9 @@ static int snd_seq_ioctl_set_client_pool (! snd_seq_write_pool_allocated(client) || info.output_pool != client->pool->size)) { if (snd_seq_write_pool_allocated(client)) { + /* is the pool in use? */ + if (atomic_read(&client->pool->counter)) + return -EBUSY; /* remove all existing cells */ snd_seq_pool_mark_closing(client->pool); snd_seq_queue_client_leave_cells(client->number);