linux-kernel - Re: [PATCH (mmotm-2008-12-02-17-08)] Introduce security_path

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Date:	Sat, 6 Dec 2008 06:16:42 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	serue@...ibm.com, jmorris@...ei.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, takedakn@...data.co.jp,
	haradats@...data.co.jp
Subject: Re: [PATCH (mmotm-2008-12-02-17-08)] Introduce
	security_path_set/clear() hooks.

On Fri, Dec 05, 2008 at 04:53:18PM -0500, Stephen Smalley wrote:
> > Right. Locations of inserting security_path_set()/security_path_clear() pairs
> > are subset of mnt_want_write()/mnt_drop_write() pairs. Thus, we can insert
> > security_path_set()/security_path_clear() pairs into
> > mnt_want_write()/mnt_drop_write() pairs, if we can tolerate performance
> > regression. According to our rough measurement, there is about 8 - 22% of
> > performance regression. But this approach needs minimum modification to the
> > existing kernel (only two hooks to be inserted).
> 
> I assume you also need separate hooks to cover the read-only open case?
> As for your performance, your implementation of mp_* is clearly
> non-optimal, so I'd expect there is plenty of room for improvement
> there.

And just what will happen if you end up with foo_mkdir() calling something
that does e.g. pathname resolution in fs-controlled private namespace and
creates/removes some files there?
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