Re: [PATCH 4.14 61/81] ALSA: seq: Protect in-kernel ioctl calls with mutex

[Greg Kroah-Hartman]

On Thu, Jun 13, 2019 at 11:02:54AM +0200, Takashi Iwai wrote:
> On Thu, 13 Jun 2019 10:33:44 +0200,
> Greg Kroah-Hartman wrote:
> > 
> > [ Upstream commit feb689025fbb6f0aa6297d3ddf97de945ea4ad32 ]
> > 
> > ALSA OSS sequencer calls the ioctl function indirectly via
> > snd_seq_kernel_client_ctl().  While we already applied the protection
> > against races between the normal ioctls and writes via the client's
> > ioctl_mutex, this code path was left untouched.  And this seems to be
> > the cause of still remaining some rare UAF as spontaneously triggered
> > by syzkaller.
> > 
> > For the sake of robustness, wrap the ioctl_mutex also for the call via
> > snd_seq_kernel_client_ctl(), too.
> > 
> > Reported-by: syzbot+e4c8abb920efa77bace9@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> 
> This commit is reverted later by commit f0654ba94e33.
> So please drop this.  The proper fix is done later by commit
> 7c32ae35fbf9 ("ALSA: seq: Cover unsubscribe_port() in list_mutex")
> 
> Ditto for 4.19.y and 5.1.y.

Now dropped everywhere, and I added 7c32ae35fbf9 ("ALSA: seq: Cover
unsubscribe_port() in list_mutex") everywhere instead.

thanks,

greg k-h