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

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Date:	Wed, 03 Dec 2008 09:13:25 -0500
From:	Stephen Smalley <sds@...ho.nsa.gov>
To:	Kentaro Takeda <takedakn@...data.co.jp>
Cc:	serue@...ibm.com, linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, haradats@...data.co.jp,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH (mmotm-2008-12-02-17-08)] Introduce
	security_path_set/clear() hooks.

On Wed, 2008-12-03 at 17:56 +0900, Kentaro Takeda wrote:
> Stephen, Serge,
> Here is the patch for introducing new security_path_set()/clear() hooks.
> 
> This patch enables LSM module to remember vfsmount's pathname so that it can 
> calculate absolute pathname in security_inode_*(). Since actual MAC can be 
> performed after DAC, there will not be any noise in auditing and learning 
> features. This patch currently assumes that the vfsmount's pathname is stored in 
> hash table in LSM module. (Should I use stack memory?)
> 
> Since security_inode_*() are not always called after security_path_set(), 
> security_path_clear() hook is needed to free the remembered pathname.

Your security_path_set()/security_path_clear() pairs look rather similar
to mnt_want_write()/mnt_drop_write() pairs.  What if you were to call
your hooks from those functions, and then you would only need to add
further hook calls in the case of read-only and execute/search checks?

-- 
Stephen Smalley
National Security Agency

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