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

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Message-ID: <20220207103009.id72sr4dtghgzp5f@work>
Date:   Mon, 7 Feb 2022 11:30:09 +0100
From:   Lukas Czerner <lczerner@...hat.com>
To:     syzbot <syzbot+138c9e58e3cb22eae3b4@...kaller.appspotmail.com>
Cc:     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 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

Thanks!
-Lukas