linux-kernel - Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

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Date:	Mon, 14 Jan 2008 14:01:19 +0000
From:	David Howells <dhowells@...hat.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	dhowells@...hat.com, Daniel J Walsh <dwalsh@...hat.com>,
	casey@...aufler-ca.com, linux-kernel@...r.kernel.org,
	selinux@...ho.nsa.gov, linux-security-module@...r.kernel.org
Subject: Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]


Stephen Smalley <sds@...ho.nsa.gov> wrote:

> > 	avc_has_perm(daemon_tsec->sid, nominated_sid,
> > 		     SECCLASS_CACHE, CACHE__USE_AS_OVERRIDE, NULL);
> > 
> > And I assume this doesn't care if one, the other or both of the two SIDs
> > mentioned are of SECCLASS_PROCESS rather than of SECCLASS_CACHE.
> 
> Right, the latter is reasonable.

Okay...  It looks like I want four security operations/hooks for cachefiles:

 (1) Check that a daemon can nominate a secid for use by the kernel to override
     the process subjective secid.

 (2) Set the secid mentioned in (1).

 (3) Check that the kernel may create files as a particular secid (this could
     be specified indirectly by specifying an inode, which would hide the secid
     inside the LSM).

 (4) Set the fscreate secid mentioned in (3).

Now, it's possible to condense (1) and (2) into a single op, and condense (3)
and (4) into a single op.  That, however, might make the ops unusable by nfsd,
which may well want to bypass the checks or do them elsewhere.

Any thoughts?

David
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