linux-kernel - Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbFindCtl

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Message-ID: <CANp29Y7wQccVBGJM_jJzrszzkE9wiHOhjdYoaPtzB=0WP0BbDA@mail.gmail.com>
Date:   Fri, 31 Mar 2023 10:43:50 +0200
From:   Aleksandr Nogikh <nogikh@...gle.com>
To:     syzbot <syzbot+7edb85bc97be9f350d90@...kaller.appspotmail.com>
Cc:     dave.kleikamp@...cle.com, jfs-discussion@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        liushixin2@...wei.com, shaggy@...nel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbFindCtl

On Thu, Mar 30, 2023 at 9:45 PM syzbot
<syzbot+7edb85bc97be9f350d90@...kaller.appspotmail.com> wrote:
>
> syzbot suspects this issue was fixed by commit:
>
> commit fad376fce0af58deebc5075b8539dc05bf639af3
> Author: Liu Shixin via Jfs-discussion <jfs-discussion@...ts.sourceforge.net>
> Date:   Thu Nov 3 03:01:59 2022 +0000
>
>     fs/jfs: fix shift exponent db_agl2size negative
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=146d74a5c80000
> start commit:   b229b6ca5abb Merge tag 'perf-tools-fixes-for-v6.1-2022-10-..
> git tree:       upstream
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a66c6c673fb555e8
> dashboard link: https://syzkaller.appspot.com/bug?extid=7edb85bc97be9f350d90
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16d5817a880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15d68cde880000
>
> If the result looks correct, please mark the issue as fixed by replying with:
>
> #syz fix: fs/jfs: fix shift exponent db_agl2size negative

It might well be possible. The patch improves the validation of
db_agl2size parameter, which affects the execution some frames up in
the crash stack trace:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/jfs/jfs_dmap.c?id=6d36c728bc2e2d632f4b0dea00df5532e20dfdab#n729

#syz fix: fs/jfs: fix shift exponent db_agl2size negative

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