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Date:   Tue, 21 Jul 2020 14:32:33 +1000
From:   Stephen Rothwell <sfr@canb.auug.org.au>
To:     Qian Cai <cai@lca.pw>
Cc:     syzbot <syzbot+75867c44841cb6373570@syzkaller.appspotmail.com>,
        Markus.Elfring@web.de, casey@schaufler-ca.com, dancol@google.com,
        hdanton@sina.com, jmorris@namei.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, stephen.smalley.work@gmail.com,
        syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk,
        yanfei.xu@windriver.com, linux-next@vger.kernel.org
Subject: Re: KASAN: use-after-free Read in userfaultfd_release (2)
Message-ID: <20200721143233.23c89f2a@canb.auug.org.au>
In-Reply-To: <20200720155024.GC7354@lca.pw>
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        <20200717150540.GB31206@lca.pw>
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Hi all,

On Mon, 20 Jul 2020 11:50:25 -0400 Qian Cai <cai@lca.pw> wrote:
>
> On Fri, Jul 17, 2020 at 11:05:41AM -0400, Qian Cai wrote:
> > On Mon, Jul 13, 2020 at 08:34:06AM -0700, syzbot wrote: =20
> > > syzbot has bisected this bug to:
> > >=20
> > > commit d08ac70b1e0dc71ac2315007bcc3efb283b2eae4
> > > Author: Daniel Colascione <dancol@google.com>
> > > Date:   Wed Apr 1 21:39:03 2020 +0000
> > >=20
> > >     Wire UFFD up to SELinux
> > >=20
> > > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=3D14a79d=
13100000
> > > start commit:   89032636 Add linux-next specific files for 20200708
> > > git tree:       linux-next
> > > final crash:    https://syzkaller.appspot.com/x/report.txt?x=3D16a79d=
13100000
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=3D12a79d131=
00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=3D64a250eba=
bc6c320
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=3D75867c44841=
cb6373570
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=3D13c4c8d=
b100000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D12cbb68f1=
00000
> > >=20
> > > Reported-by: syzbot+75867c44841cb6373570@syzkaller.appspotmail.com
> > > Fixes: d08ac70b1e0d ("Wire UFFD up to SELinux")
> > >=20
> > > For information about bisection process see: https://goo.gl/tpsmEJ#bi=
section =20
> >=20
> > This is rather easy to reproduce here, =20
>=20
> James, Stephen, can you drop this patch? Daniel's email was bounced, and =
Viro
> mentioned the patch could be quite bad,
>=20
> https://lore.kernel.org/lkml/20200719165746.GJ2786714@ZenIV.linux.org.uk/

I have reverted that commit in linux-next today.

--=20
Cheers,
Stephen Rothwell

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