linux-kernel - Re: [PATCH 12/19] CacheFiles: Permit a process's create SID to be overridden

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Date:	Wed, 15 Nov 2006 16:23:33 +0000
From:	David Howells <dhowells@...hat.com>
To:	James Morris <jmorris@...ei.org>
Cc:	David Howells <dhowells@...hat.com>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...l.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	trond.myklebust@....uio.no, selinux@...ho.nsa.gov,
	linux-kernel@...r.kernel.org, aviro@...hat.com, steved@...hat.com
Subject: Re: [PATCH 12/19] CacheFiles: Permit a process's create SID to be overridden 

James Morris <jmorris@...ei.org> wrote:

> Well, the value can be changed at any time, so you could be using a 
> temporary fscreate value, or your new value could be overwritten 
> immediately by writing to /proc/$$/attr/fscreate

Ah.  Hmmm.  By whom?  In selinux_setprocattr():

	if (current != p) {
		/* SELinux only allows a process to change its own
		   security attributes. */
		return -EACCES;
	}

But current busy inside the cache and can't do this.

> I think we need to add a separate field for this purpose, which can only 
> be written to via the in-kernel API and overrides fscreate.

So, like my acts-as security ID patch?

Would it still need to be controlled by MAC policy in that case?  Doing so is
a bit of a pain as it means I have a whole bunch of extra failures I still
need to check for, and the race in which the rules might change is still a
possibility I have to deal with.

David
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