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From:   Filipe Manana <fdmanana@gmail.com>
Date:   Fri, 8 Jan 2021 14:22:00 +0000
Message-ID: <CAL3q7H63XwdxmHgTRZthh6xYtg1uyqAK3apbrwxobRQ660U+JA@mail.gmail.com>
Subject: Re: KASAN: null-ptr-deref Write in start_transaction
To:     syzbot <syzbot+6700bca07dff187809c4@syzkaller.appspotmail.com>
Cc:     Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
        Filipe David Borba Manana <fdmanana@suse.com>,
        Josef Bacik <josef@toxicpanda.com>,
        linux-btrfs <linux-btrfs@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        mingo@kernel.org, mingo@redhat.com, peterz@infradead.org,
        rostedt@goodmis.org, syzkaller-bugs@googlegroups.com,
        will@kernel.org
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On Thu, Jan 7, 2021 at 1:13 PM syzbot
<syzbot+6700bca07dff187809c4@syzkaller.appspotmail.com> wrote:
>
> syzbot suspects this issue was fixed by commit:
>
> commit f30bed83426c5cb9fce6cabb3f7cc5a9d5428fcc
> Author: Filipe Manana <fdmanana@suse.com>
> Date:   Fri Nov 13 11:24:17 2020 +0000
>
>     btrfs: remove unnecessary attempt to drop extent maps after adding in=
line extent
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=3D13ddc30b50=
0000
> start commit:   521b619a Merge tag 'linux-kselftest-kunit-fixes-5.10-rc3'=
 ..
> git tree:       upstream
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3D61033507391c7=
7ff
> dashboard link: https://syzkaller.appspot.com/bug?extid=3D6700bca07dff187=
809c4
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=3D14a07ab2500=
000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D10fe69c650000=
0
>
> If the result looks correct, please mark the issue as fixed by replying w=
ith:
>
> #syz fix: btrfs: remove unnecessary attempt to drop extent maps after add=
ing inline extent

Nop, it can't be this change.

What should fix it should be the following commit:

commit ecfdc08b8cc65d737eebc26a1ee1875a097fd6a0
Author: Goldwyn Rodrigues <rgoldwyn@suse.com>
Date:   Thu Sep 24 11:39:21 2020 -0500

    btrfs: remove dio iomap DSYNC workaround

Thanks.


>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisect=
ion


--=20
Filipe David Manana,

=E2=80=9CWhether you think you can, or you think you can't =E2=80=94 you're=
 right.=E2=80=9D