Re: [PATCH 4.19 06/48] ALSA: seq: oss: Serialize ioctls

From: Greg Kroah-Hartman
Date: Mon Aug 10 2020 - 13:29:28 EST

On Mon, Aug 10, 2020 at 06:37:17PM +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.

Please discuss code architecture decisions on the mailing list for the
subsystem/patch. Doing it in random stable backports does not help out
as all of the developers involved are not copied here.


greg k-h