linux-kernel - Re: [patch 0/8] unprivileged mount syscall

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Date:	Wed, 11 Apr 2007 22:27:12 +0800
From:	Ian Kent <raven@...maw.net>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Miklos Szeredi <miklos@...redi.hu>, hpa@...or.com,
	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	util-linux-ng@...r.kernel.org, containers@...ts.osdl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 0/8] unprivileged mount syscall

On Wed, 2007-04-11 at 09:26 -0500, Serge E. Hallyn wrote:
> Quoting Ian Kent (raven@...maw.net):
> > 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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