Re: [RCF] [PATCH] unprivileged mount/umount

[Jamie Lokier <jamie@shareable.org>]

Miklos Szeredi wrote:
> > > > How about a new clone option "CLONE_NOSUID"?
> > > 
> > > IMO, the clone call ist the wrong place to create namespaces. It should be
> > > deprecated by a mkdir/chdir-like interface.
> > 
> > And the mkdir/chdir interface already exists, see "cd /proc/NNN/root".
> 
> That's the chdir part.
> 
> The mkdir part is clone() or unshare().
> 
> How else do you propose to create new namespaces?

This is not a proposal - I'm not saying it's pretty - but a suggestion
that you can use today.

Use clone(), and then have the child task open "/" and pass that file
descriptor back to the parent process using a unix socket.  The child
can exit and the parent can use the new namespace how it likes.  Short
and sweet, and you can create as many namespaces as you like :)

That's mkdir done.

You can't do a lot with the new namespace, because of the security
restrictions on mount() on a foreign namespace.  That's what I meant
about the "small fixes" - get rid of the current->namespace checks and
it'll be usable.

I don't see the purpose of current->namespace and the associated mount
restrictions at all.  I asked Al Viro what it's for, but haven't seen
a reply :(  IMHO current->namespace should simply be removed, because the
"current namespace" is represented just fine by
current->fs->rootmnt->mnt_namespace.

-- Jamie