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    SubjectRe: [PATCH 4.14 61/81] ALSA: seq: Protect in-kernel ioctl calls with mutex
    On Thu, 13 Jun 2019 17:39:46 +0200,
    Sasha Levin wrote:
    >
    > On Thu, Jun 13, 2019 at 11:13:55AM +0200, Takashi Iwai wrote:
    > >On Thu, 13 Jun 2019 11:11:22 +0200,
    > >Greg Kroah-Hartman wrote:
    > >>
    > >> 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@syzkaller.appspotmail.com
    > >> > > Signed-off-by: Takashi Iwai <tiwai@suse.de>
    > >> > > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > >> >
    > >> > 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!
    > >
    > >BTW, do we have a systematic check whether the selected stable commit
    > >is reverted in a later commit? At least, you can track it as long as
    > >Fixes tag is properly set.
    >
    > I have that scripting in place, and I usually check it once before I
    > send the initial reviews and then once Greg does the -rc release.

    OK, good to hear. So this time must be some exceptional error.


    thanks,

    Takashi

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