linux-kernel - Re: [PATCH] fs: Add additional checks for block devices during mount

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Message-ID: <20250719041709.GI2580412@ZenIV>
Date: Sat, 19 Jul 2025 05:17:09 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Zizhi Wo <wozizhi@...wei.com>
Cc: jack@...e.com, brauner@...nel.org, axboe@...nel.dk, hch@....de,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH] fs: Add additional checks for block devices during mount

On Sat, Jul 19, 2025 at 10:44:03AM +0800, Zizhi Wo wrote:

> mkfs.ext4 -F /dev/sdb
> mount /dev/sdb /mnt
> mknod /dev/test b 8 16    # [sdb 8:16]
> echo 1 > /sys/block/sdb/device/delete
> mount /dev/test /mnt1    # -> mount success
> 
> Therefore, it is necessary to add an extra check. Solve this problem by
> checking disk_live() in super_s_dev_test().

That smells like a wrong approach...  You are counting upon the failure
of setup_bdev_super() after the thing is forced on the "no reuse" path,
and that's too convoluted and brittle...