Re: [patch 00/10] mount ownership and unprivileged mount syscall (v8)

Miklos Szeredi
2008-02-23T17:33:41Z

> On Mon, Feb 18, 2008 at 12:47:59PM +0100, Miklos Szeredi wrote:
> > So what should I do?
> >
> > Would Al be wanting to merge this into his VFS tree? (Can't find it
> > on git.kernel.org yet, BTW.)
>
> FWIW, it's on hera right now, should propagate to git.kernel.org in a few.
>
> Branches I'd pushed there: vfs-fixes.b0 and ro-bind.b0. The latter is
> on top of the former. There will be more, but that at least takes care
> of the most urgent stuff. Again, apologies for things being too damn
> slow ;-/
>
> As for the unprivileged mounts...
> a) why do we lose them on clone() in new namespace? Bloody
> inconvenient, to put it mildly.
> b) why do we prohibit all kinds of remount?

I wanted to get the basics right, before thinking about these details.
But getting the semantics of a) right before this is merged is a good
idea, of course... So I'll have to think about that.

The remount stuff can wait (especially if there will be a new mount
API for this kind of thing).

> c) just what is limited by that sysctl? AFAICS, rbind is allowed
> if mountpoint is on user vfsmount and it seems to create vfsmounts without
> eating into that limit just fine... What's the point of limiting the
> amount of vfsmounts marked user when you do not limit the number of vfsmount
> one can allocate?

The limit is there, so that unprivileged users cannot create insane
number of mounts. It's just a safety thing, analogous to
/proc/sys/fs/file-max.

Thanks for looking at this.

Miklos