Re: [patch 0/8] unprivileged mount syscall

Ian Kent
2007-04-11T14:27:12Z

On Wed, 2007-04-11 at 09:26 -0500, Serge E. Hallyn wrote:
> Quoting Ian Kent (raven-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org):
> > On Wed, 2007-04-11 at 12:48 +0200, Miklos Szeredi wrote:
> > > > > >>
> > > > > >> - users can use bind mounts without having to pre-configure them in
> > > > > >> /etc/fstab
> > > > > >>
> > > > >
> > > > > This is by far the biggest concern I see. I think the security
> > > > > implication of allowing anyone to do bind mounts are poorly understood.
> > > >
> > > > And especially so since there is no way for a filesystem module to veto
> > > > such requests.
> > >
> > > The filesystem can't veto initial mounts based on destination either.
> > > I don't think it's up to the filesystem to police bind/move mounts in
> > > any way.
> >
> > But if a filesystem can't or the developer thinks that it shouldn't for
> > some reason, support bind/move mounts then there should be a way for the
>
> Can you list some valid reasons why an fs could care where it is
> mounted? The only thing I could think of is a stackable fs, but it
> shouldn't care whether it is overlay-mounted or not.

For my part, autofs and autofs4.
Moving or binding isn't valid.
I tried to design that limitation out version 5 but wasn't able to.
In time I probably can but couldn't continue to support older versions.

>
> thanks,
> -serge
>
> > filesystem to tell the kernel that.
> >
> > Surely a filesystem is in a good position to be able to decide if a
> > mount request "for it" should be allowed to continue based on it's "own
> > situation and capabilities".
> >
> > Ian
> >
> >
> >
> > -
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