Re: [PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace

[Al Viro]

On Thu, May 21, 2026 at 10:28:56AM +0300, Denis Arefev wrote:
> The bdev pseudo-filesystem is an internal kernel filesystem with which
> userspace should not interfere. Unregister it so that userspace cannot
> even attempt to mount it.
> 
> This fixes a bug [1] that occurs when attempting to access files,
> because the system call move_mount() uses pointers declared in the
> inode_operations structure, which for the bdev pseudo-filesystem
> are always equal to 0. `inode->i_op = &empty_iops;`

What?  init_pseudo() sets SB_NOUSER; what are you talking about?
And assuming you've somehow managed to mount the sucker, which
->i_op method had been accessed?