Bug#1106070: linux-image-6.12.29-amd64: loop device cannot mount live squashfs any more

[Roland Clobus]

Hello Bastian,

On 19/05/2025 12:49, Bastian Blank wrote:

On Mon, May 19, 2025 at 12:15:10PM +0200, Roland Clobus wrote:

It appears that the loopback device cannot be used any more with the mount
/run/live/medium (which is on /dev/sr0).

/run/live/medium is isofs?

Indeed, it uses the iso9660 kernel module.

I would expect this commit:

commit 184b147b9f7f07577567a80fcc9314f2bd0b0b00
Author: Lizhi Xu <lizhi...@windriver.com>
Date:   Mon Apr 28 22:36:26 2025 +0800

     loop: Add sanity check for read/write_iter

     in this issue.
     So before calling them, first confirm that the interface is supported and
     then call it.

     of their used caused szybot to be able to hit this issue.

     Reported-by: syzbot+6af973a3b8dfd2fae...@syzkaller.appspotmail.com
     Closes: https://syzkaller.appspot.com/bug?extid=6af973a3b8dfd2faefdc
     Signed-off-by: Lizhi Xu <lizhi...@windriver.com>
     Reviewed-by: Christoph Hellwig <h...@lst.de>
     Link: 
https://lore.kernel.org/r/20250428143626.3318717-1-lizhi...@windriver.com
     Signed-off-by: Jens Axboe <ax...@kernel.dk>
     Signed-off-by: Sasha Levin <sas...@kernel.org>

[ Upstream commit f5c84eff634ba003326aa034c414e2a9dcb7c6a7 ] Some file systems do not support read_iter/write_iter, such as selinuxfs It is releavant in that vfs_iter_read/write have the check, and removal Fixes: f2fed441c69b ("loop: stop using vfs_iter__{read,write} for buffered I/O")

This looks like this change could have caused the issue.
How to proceed?

With kind regards,
Roland Clobus

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