linux-kernel - Re: [syzbot] general protection fault in ext4_fill

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Message-ID: <CACT4Y+Z-R1swsyGrdgy89zHvmAa8tsBVE=mLngsapr5qPre9ZQ@mail.gmail.com>
Date:   Mon, 7 Feb 2022 12:29:30 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     syzbot <syzbot+138c9e58e3cb22eae3b4@...kaller.appspotmail.com>,
        adilger.kernel@...ger.ca, cmaiolino@...hat.com,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, nathan@...nel.org, ndesaulniers@...gle.com,
        syzkaller-bugs@...glegroups.com, tytso@....edu
Subject: Re: [syzbot] general protection fault in ext4_fill_super

On Mon, 7 Feb 2022 at 11:30, Lukas Czerner <lczerner@...hat.com> wrote:
>
> On Sat, Feb 05, 2022 at 02:39:06PM -0800, syzbot wrote:
> > syzbot has bisected this issue to:
> >
> > commit cebe85d570cf84804e848332d6721bc9e5300e07
> > Author: Lukas Czerner <lczerner@...hat.com>
> > Date:   Wed Oct 27 14:18:56 2021 +0000
> >
> >     ext4: switch to the new mount api
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14902978700000
> > start commit:   0457e5153e0e Merge tag 'for-linus' of git://git.kernel.org..
> > git tree:       upstream
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=16902978700000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=12902978700000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=cd57c0f940a9a1ec
> > dashboard link: https://syzkaller.appspot.com/bug?extid=138c9e58e3cb22eae3b4
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f7004fb00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=178cf108700000
> >
> > Reported-by: syzbot+138c9e58e3cb22eae3b4@...kaller.appspotmail.com
> > Fixes: cebe85d570cf ("ext4: switch to the new mount api")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> >
>
> I believe that this has been fixed with upstream commit
>
> commit 7c268d4ce2d3761f666a9950b029c8902bfab710
> Author: Lukas Czerner <lczerner@...hat.com>
> Date:   Wed Jan 19 14:02:09 2022 +0100
>
>     ext4: fix potential NULL pointer dereference in ext4_fill_super()
>
>     By mistake we fail to return an error from ext4_fill_super() in case
>     that ext4_alloc_sbi() fails to allocate a new sbi. Instead we just set
>     the ret variable and allow the function to continue which will later
>     lead to a NULL pointer dereference. Fix it by returning -ENOMEM in the
>     case ext4_alloc_sbi() fails.
>
>     Fixes: cebe85d570cf ("ext4: switch to the new mount api")
>     Reported-by: kernel test robot <lkp@...el.com>
>     Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
>     Signed-off-by: Lukas Czerner <lczerner@...hat.com>
>     Link: https://lore.kernel.org/r/20220119130209.40112-1-lczerner@redhat.com
>     Signed-off-by: Theodore Ts'o <tytso@....edu>
>     Cc: stable@...nel.org


Let's tell syzbot then:

#syz fix: ext4: fix potential NULL pointer dereference in ext4_fill_super()

Thanks