On Mon, 10 Aug 2020 18:37:17 +0200, Pavel Machek wrote: > > Hi! > > > commit 80982c7e834e5d4e325b6ce33757012ecafdf0bb upstream. > > > > Some ioctls via OSS sequencer API may race and lead to UAF when the > > port create and delete are performed concurrently, as spotted by a > > couple of syzkaller cases. This patch is an attempt to address it by > > serializing the ioctls with the existing register_mutex. > > > > Basically OSS sequencer API is an obsoleted interface and was designed > > without much consideration of the concurrency. There are very few > > applications with it, and the concurrent performance isn't asked, > > hence this "big hammer" approach should be good enough. > > That really is a "big hammer". And I believe it is too big. > > In particular, do we need to drop the lock while sleeping in > SNDCTL_SEQ_SYNC: => snd_seq_oss_writeq_sync ? Well, do you see any issue with this for really used applications? If yes, I'd happily take a look and give finer locking. thanks, Takashi
