Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <0000000000001fe79005afbf52ea@google.com> <20200930165756.GQ6756@twin.jikos.cz>
 <20200930180522.GR6756@twin.jikos.cz>
In-Reply-To: <20200930180522.GR6756@twin.jikos.cz>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 1 Oct 2020 15:05:44 +0200
Message-ID: <CACT4Y+b6ctH447Hy9JuP1hF5MSV368WAB2tXz8xfi-5ZM-=tOg@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>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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=10a0a8bb900000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=ffe85b197a57c180
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0
> > > 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 the commit:
> > > Reported-by: syzbot+582e66e5edf36a22c7b0@syzkaller.appspotmail.com
> >
> > #syz fix: btrfs: fix overflow when copying corrupt csums for a message
>
> 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