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

[Bastian Blank <waldi@debian.org>]

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?

I would expect this commit:

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

    loop: Add sanity check for read/write_iter
    
    [ Upstream commit f5c84eff634ba003326aa034c414e2a9dcb7c6a7 ]
    
    Some file systems do not support read_iter/write_iter, such as selinuxfs
    in this issue.
    So before calling them, first confirm that the interface is supported and
    then call it.
    
    It is releavant in that vfs_iter_read/write have the check, and removal
    of their used caused szybot to be able to hit this issue.
    
    Fixes: f2fed441c69b ("loop: stop using vfs_iter__{read,write} for buffered I/O")
    Reported-by: syzbot+6af973a3b8dfd2faefdc@syzkaller.appspotmail.com
    Closes: https://syzkaller.appspot.com/bug?extid=6af973a3b8dfd2faefdc
    Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Link: https://lore.kernel.org/r/20250428143626.3318717-1-lizhi.xu@windriver.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

Bastian

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