Re: [PATCH] vfs: move_mount: reject moving kernel internal mounts

[Al Viro]

On Mon, Jul 01, 2019 at 08:38:10AM +0100, David Howells wrote:
> Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> 
> > 	/* The thing moved must be mounted... */
> > 	if (!is_mounted(old_path->mnt))
> > 		goto out;
> 
> Um...  Doesn't that stuff up fsmount()?

Nope - check is_mounted() definition.  Stuff in anon namespace
*is* mounted there, so that's not a problem.

FWIW, is_mounted() would've been better off spelled as
ns != NULL && ns != MNT_NS_INTERNAL; the use of IS_ERR_OR_NULL
in there works, but is unidiomatic and I don't think it yields
better code...