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 ?
Best regards,
Pavel
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