linux-kernel - Re: [syzbot] [overlayfs?] general protection fault in ovl_encode_real

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Message-ID: <CAOQ4uxhgWHoauPKUDfmuvu9uyMC23gkKVgi98R7XgX6s+fuh7w@mail.gmail.com>
Date:   Tue, 3 Oct 2023 10:45:11 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     syzbot <syzbot+2208f82282740c1c8915@...kaller.appspotmail.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-unionfs@...r.kernel.org, miklos@...redi.hu,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [overlayfs?] general protection fault in ovl_encode_real_fh

On Tue, Oct 3, 2023 at 7:56 AM syzbot
<syzbot+2208f82282740c1c8915@...kaller.appspotmail.com> wrote:
>
> syzbot has bisected this issue to:
>
> commit 16aac5ad1fa94894b798dd522c5c3a6a0628d7f0
> Author: Amir Goldstein <amir73il@...il.com>
> Date:   Sun Apr 23 16:02:04 2023 +0000
>
>     ovl: support encoding non-decodable file handles
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11972062680000
> start commit:   8a749fd1a872 Linux 6.6-rc4
> git tree:       upstream
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=13972062680000
> console output: https://syzkaller.appspot.com/x/log.txt?x=15972062680000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=57da1ac039c4c78a
> dashboard link: https://syzkaller.appspot.com/bug?extid=2208f82282740c1c8915
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14877eb2680000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13b701f6680000
>
> Reported-by: syzbot+2208f82282740c1c8915@...kaller.appspotmail.com
> Fixes: 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

That was a stupid braino.

Reproducer is simple I added test coverage to LTP:
https://github.com/amir73il/ltp/commits/ovl_encode_fid

and pushed a fix to

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs.git
ovl-fixes