linux-kernel - Re: [syzbot] [erofs?] [fat?] WARNING in erofs_kill

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Message-ID: <9b57e5f7-62b6-fd65-4dac-a71c9dc08abc@linux.alibaba.com>
Date:   Mon, 31 Jul 2023 18:58:14 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Christoph Hellwig <hch@....de>,
        syzbot <syzbot+69c477e882e44ce41ad9@...kaller.appspotmail.com>
Cc:     brauner@...nel.org, chao@...nel.org, huyue2@...lpad.com,
        jack@...e.cz, jefflexu@...ux.alibaba.com, linkinjeon@...nel.org,
        linux-erofs@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, sj1557.seo@...sung.com,
        syzkaller-bugs@...glegroups.com, xiang@...nel.org
Subject: Re: [syzbot] [erofs?] [fat?] WARNING in erofs_kill_sb

On 2023/7/31 17:37, Christoph Hellwig wrote:
> On Mon, Jul 31, 2023 at 12:57:58AM -0700, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    d7b3af5a77e8 Add linux-next specific files for 20230728
> 
> Hmm, the current linux-next tree does not seem to have that commit ID
> any more, and the line numbers don't match up.  I think it is the
> WARN_ON for the magic, which could probably be just removed.  I'll
> try the reproducers when I find a bit more time.

Previously, deactivate_locked_super() or .kill_sb() will only be
called after fill_super is called, and .s_magic will be set at
the very beginning of erofs_fc_fill_super().

After ("fs: open block device after superblock creation"), such
convension is changed now.  Yet at a quick glance,

WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);

in erofs_kill_sb() can be removed since deactivate_locked_super()
will also be called if setup_bdev_super() is falled.  I'd suggest
that removing this WARN_ON() in the related commit, or as
a following commit of the related branch of the pull request if
possible.

Thanks,
Gao Xiang