linux-kernel - Re: implement-file-posix-capabilities.patch

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Date:	Sun, 24 Jun 2007 12:18:52 -0400 (EDT)
From:	James Morris <jmorris@...ei.org>
To:	"Serge E. Hallyn" <serge@...lyn.com>
cc:	Andrew Morgan <morgan@...nel.org>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Andrew Morgan <agm@...gle.com>, casey@...aufler-ca.com,
	Andrew Morton <akpm@...gle.com>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	linux-security-module@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: implement-file-posix-capabilities.patch

On Sun, 24 Jun 2007, Serge E. Hallyn wrote:

> > 2) Allocate capability bit-31 for CAP_SETFCAP, and use it to gate
> > whether the user can set this xattr on a file or not. CAP_SYS_ADMIN is
> > way too overloaded and this functionality is special.
> 
> The functionality is special, but someone with CAP_SYS_ADMIN can always
> unload the capability module and create the security.capability xattr
> using the dummy module.
> 
> If we do add this cap, do we want to make it apply to all security.*
> xattrs?

The underlying issue here is the notion of security mechanisms which are 
built as loadable modules.  It's not useful for any in-tree users, and 
introduces several unnecessary problems which then need to be addressed.

A better approach would be to make LSM a statically linked interface.

This would also allow us to unexport the LSM symbols and reduce the API 
abuse by third-party modules.


- James
-- 
James Morris
<jmorris@...ei.org>
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