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

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Message-Id: <E1Hb0CH-0000nX-00@dorka.pomaz.szeredi.hu>
Date:	Mon, 09 Apr 2007 22:10:41 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	serue@...ibm.com
CC:	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	containers@...ts.osdl.org, util-linux-ng@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxram@...ibm.com
Subject: Re: [patch 0/8] unprivileged mount syscall

> > The one in pam-0.99.6.3-29.1 in opensuse-10.2 is totally broken.  Are
> > you interested in the details?  I can reproduce it, but forgot to note
> > down the details of the brokenness.
> 
> I don't know how far removed that is from the one being used by redhat,
> but assuming it's the same, then redhat-lspp@...hat.com will be
> very interested.

OK.

> >  - user namespace setup: what if user has multiple sessions?
> > 
> >    1) namespaces are shared?  That's tricky because the session needs to
> >    be a child of a namespace server, not of login.  I'm not sure PAM
> >    can handle this
> > 
> >    2) or mounts are copied on login?  That's not possible currently,
> >    as there's no way to send a mount between namespaces.  Also it's
> >    tricky to make sure that new mounts are also shared
> 
> See toward the end of the 'shared subtrees' OLS paper from last year for
> a suggestion on how to let users effectively 'log in to' an existing
> private mounts ns.

This?

  1. create a new namespace
  2. bind /share/$USER to /share
  3. for each pair ($who, $what) such that
     /share/$USER/$who/$what exists, look
     in /share/$who/allowed for "peer $what
     $USER" or "slave $what $USER". If the
     former is found, rbind /share/$who/$what
     on /share/$USER/$who/$what; if the
     latter is found, do the same and
     follow with marking subtree under
     /share/$USER/$who/$what as slave.
  4. rbind /share/$USER to /share
  5. mark subtree under /share as private.
  6. umount -l /share

Well, someone please explain using short words, because I don't
understand at all.

Thanks,
Miklos
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