linux-kernel - Re: WARNING: filesystem loop5 was created with 512 inodes, the real maximum is 511, mounting anyway

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Date:   Tue, 1 Dec 2020 08:47:27 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     syzbot <syzbot+3fd34060f26e766536ff@...kaller.appspotmail.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: WARNING: filesystem loop5 was created with 512 inodes, the real
 maximum is 511, mounting anyway

On Tue, Dec 1, 2020 at 2:03 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> On 11/30/20 12:43 AM, Dmitry Vyukov wrote:
> > On Mon, Nov 30, 2020 at 5:29 AM Randy Dunlap <rdunlap@...radead.org> wrote:
> >>
> >> On 11/27/20 4:32 AM, syzbot wrote:
> >>> Hello,
> >>>
> >>> syzbot found the following issue on:
> >>>
> >>> HEAD commit:    418baf2c Linux 5.10-rc5
> >>> git tree:       upstream
> >>> console output: https://syzkaller.appspot.com/x/log.txt?x=171555b9500000
> >>> kernel config:  https://syzkaller.appspot.com/x/.config?x=b81aff78c272da44
> >>> dashboard link: https://syzkaller.appspot.com/bug?extid=3fd34060f26e766536ff
> >>> compiler:       gcc (GCC) 10.1.0-syz 20200507
> >>>
> >>> Unfortunately, I don't have any reproducer for this issue yet.
> >>>
> >>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >>> Reported-by: syzbot+3fd34060f26e766536ff@...kaller.appspotmail.com
> >>>
> >>> BFS-fs: bfs_fill_super(): loop5 is unclean, continuing
> >>> BFS-fs: bfs_fill_super(): WARNING: filesystem loop5 was created with 512 inodes, the real maximum is 511, mounting anyway
> >>> BFS-fs: bfs_fill_super(): Last block not available on loop5: 120
> >>> BFS-fs: bfs_fill_super(): loop5 is unclean, continuing
> >>> BFS-fs: bfs_fill_super(): WARNING: filesystem loop5 was created with 512 inodes, the real maximum is 511, mounting anyway
> >>> BFS-fs: bfs_fill_super(): Last block not available on loop5: 120
> >>>
> >>>
> >>> ---
> >>> This report is generated by a bot. It may contain errors.
> >>> See https://goo.gl/tpsmEJ for more information about syzbot.
> >>> syzbot engineers can be reached at syzkaller@...glegroups.com.
> >>>
> >>> syzbot will keep track of this issue. See:
> >>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >>>
> >>
> >> Hi,
> >> Can you provide the BFS image file that is being mounted?
> >> (./file0 I think.)
> >>
> >> --
> >> ~Randy
> >
> >
> > Hi Randy,
> >
> > I see this bug was reported with a reproducer:
> > https://syzkaller.appspot.com/bug?id=a32ebd5db2f7c957b82cf54b97bdecf367bf0421
> > I assume it's a dup of this one.
>
> Sure, looks the same.
>
> > If you need the image itself, you can dump it to a file in the C
> > reproducer inside of syz_mount_image before mount call.
>
> Yes, got that.
>
> What outcome or result are you looking for here?
> Or what do you see as the problem?

Hi Randy,

"WARNING:" in kernel output is supposed to mean a kernel source bug.
Presence of that kernel bug is what syzbot has reported.

Note: the bug may be a misuse of the "WARNING:" for invalid user
inputs in output as well :)