linux-kernel - Re: [PATCH 1/4] proc: fix NULL ->i

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Message-Id: <1195572157.20910.40.camel@moss-spartans.epoch.ncsc.mil>
Date:	Tue, 20 Nov 2007 10:22:37 -0500
From:	Stephen Smalley <sds@...ho.nsa.gov>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Alexey Dobriyan <adobriyan@...ru>, akpm@...l.org,
	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	devel@...nvz.org, James Morris <jmorris@...ei.org>,
	Eric Paris <eparis@...isplace.org>
Subject: Re: [PATCH 1/4] proc: fix NULL ->i_fop oops

On Tue, 2007-11-20 at 15:17 +0000, Christoph Hellwig wrote:
> On Tue, Nov 20, 2007 at 10:05:05AM -0500, Stephen Smalley wrote:
> > > Nice, getting rid of this is a very good step formwards.  Unfortunately
> > > we have another copy of this junk in
> > > security/selinux/selinuxfs.c:sel_remove_entries() which would need the
> > > same treatment.
> > 
> > Can't just be dropped completely for selinux - we need a way to drop
> > obsolete entries from the prior policy when we load a new policy.
> > 
> > Is the only real problem here the clearing of f_op?  If so, we can
> > likely remove that from sel_remove_entries() without harm, and fix the
> > checks for it to use something more reliable.
> 
> f_op removal is the biggest issue.  It can't really work and this is the
> last instance.  But in general having some half-backed attempts at revoke
> is never a good idea.

Yes, we're not trying to revoke per se, but just re-populate a set of
directories that represent elements of policy state on a policy
reload.  /selinux/booleans is one example - a directory with one entry
per policy boolean defined by the policy.  Old directory tree gets torn
down on each policy reload and replaced.

-- 
Stephen Smalley
National Security Agency

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