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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 1 Oct 2020 15:08:34 +0200
Message-ID: <CACT4Y+bQdT_eOcE-jOJQQFR_xi14YwBQUosuUTNq1t-k5JSFJQ@mail.gmail.com>
Subject: Re: KASAN: use-after-free Read in btrfs_scan_one_device
To:     dsterba@suse.cz,
        syzbot <syzbot+582e66e5edf36a22c7b0@syzkaller.appspotmail.com>,
        Chris Mason <clm@fb.com>, dsterba@suse.com,
        Josef Bacik <josef@toxicpanda.com>,
        linux-btrfs@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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On Thu, Oct 1, 2020 at 3:05 PM Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Wed, Sep 30, 2020 at 8:06 PM David Sterba <dsterba@suse.cz> wrote:
> >
> > On Wed, Sep 30, 2020 at 06:57:56PM +0200, David Sterba wrote:
> > > On Sun, Sep 20, 2020 at 07:12:14AM -0700, syzbot wrote:
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit:    eb5f95f1 Merge tag 's390-5.9-6' of git://git.kernel=
.org/pu..
> > > > git tree:       upstream
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=3D10a0a8b=
b900000
> > > > kernel config:  https://syzkaller.appspot.com/x/.config?x=3Dffe85b1=
97a57c180
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3D582e66e5e=
df36a22c7b0
> > > > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > > >
> > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to th=
e commit:
> > > > Reported-by: syzbot+582e66e5edf36a22c7b0@syzkaller.appspotmail.com
> > >
> > > #syz fix: btrfs: fix overflow when copying corrupt csums for a messag=
e
> >
> > Johannes spotted that this is not the right fix for this report, I don'=
t
> > know how to tell syzbot to revert the 'fix:' command, there isn't
> > 'unfix' (like there's 'undup').
>
> Hi David,
>
> I've added "unfix" command:
> https://github.com/google/syzkaller/pull/2156
>
> Let's give it a try:
> #syz unfix
>
> Thanks

Voil=C3=A0! Unfixed:
https://syzkaller.appspot.com/bug?extid=3D582e66e5edf36a22c7b0