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

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Date:   Mon, 31 Jul 2023 13:16:22 +0200
From:   Christoph Hellwig <hch@....de>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     Christoph Hellwig <hch@....de>,
        syzbot <syzbot+69c477e882e44ce41ad9@...kaller.appspotmail.com>,
        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 Mon, Jul 31, 2023 at 06:58:14PM +0800, Gao Xiang wrote:
> 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.

Agreed.  I wonder if we should really call into ->kill_sb before
calling into fill_super, but I need to carefull look into the
details.