linux-kernel - Re: TOMOYO Linux Security Goal

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Date:	Mon, 31 Dec 2007 09:17:12 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	serue@...ibm.com, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: TOMOYO Linux Security Goal

Quoting Tetsuo Handa (penguin-kernel@...ove.SAKURA.ne.jp):
> Hello.
> 
> Serge E. Hallyn wrote:
> > > > >   * namespace manipulation. (i.e. mount()/umount()/pivot_root())
> > > > 
> > > > do you track mounts namespace cloning?
> > > > 
> > > Yes. TOMOYO can recognize mount operation with the following flags.
> > > 
> > >   --bind --move --remount
> > >   --make-unbindable --make-private --make-slave --make-shared
> > 
> > No, I mean clone(CLONE_NEWNS) and unshare(CLONE_NEWNS).  Without
> > tracking those, it seems like a convoluted sequence of mounting,
> > unmonting, and mount sharing and unsharing could potentially confuse
> > your policy or your admins...
> Oh, I see. TOMOYO doesn't track clone() and unshare().
> 
> > I haven't fully thought it through.  But at least if an admin makes a
> > policy update with an expectation that all processes have the same mount
> > trees the result could be unsafe.
> TOMOYO doesn't expect that all processes have the same mount trees.
> But TOMOYO expects that the mount trees won't change unless one of mount()/
> umount()/pivot_root() are called.
> Does a process get different mount trees by just calling clone() or unshare()?
> My understanding is that clone() or unshare() disables propergation of
> mount tree changes when somebody calls mount() or umount() or pivot_root().

Yes, with further propagation rules possible.

> > > Speak of bind mounts, there comes vfsmount problem.
> > > AppArmor has been proposing patches to pass "struct vfsmount" parameter to
> > > VFS helper functions and LSM hooks so that AppArmor/TOMOYO can determine
> > > which pathname was requested in the bind-mounted environment.
> > > Without the vfsmount patches, we can't calculate pathname without the risk of
> > > AB-BA deadlock (if namespace_sem held) or crash (if namespace_sem not held).
> > > I think we should start discussing how the vfsmount patches can be merged.
> > > I'm sad to see no response for AppArmor's posting
> > > at http://lkml.org/lkml/2007/12/20/182 .
> > 
> > If the patches solve your problem, and you respond saying "TOMOYO needs
> > these patches too", it just might get the thread going.
> > 
> I'll say it when I submit patches.
> 
> Regards.
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