From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCH] xsm/flask: Handle policy load failures properly Date: Mon, 23 Feb 2015 18:00:18 +0000 Message-ID: <20150223180018.GF20083@zion.uk.xensource.com> References: <1424707899-18101-1-git-send-email-dgdegra@tycho.nsa.gov> <20150223164823.GD20083@zion.uk.xensource.com> <54EB6930.2040703@tycho.nsa.gov> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YPxJ6-0002SW-TM for xen-devel@lists.xenproject.org; Mon, 23 Feb 2015 18:00:39 +0000 Content-Disposition: inline In-Reply-To: <54EB6930.2040703@tycho.nsa.gov> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Daniel De Graaf Cc: xen-devel@lists.xenproject.org, julien.grall@linaro.org, Wei Liu List-Id: xen-devel@lists.xenproject.org On Mon, Feb 23, 2015 at 12:53:52PM -0500, Daniel De Graaf wrote: > On 02/23/2015 11:48 AM, Wei Liu wrote: > >On Mon, Feb 23, 2015 at 11:11:39AM -0500, Daniel De Graaf wrote: > >[...] > >>- if ( flask_enforcing ) > >>+ if ( ret && policy_size ) > >>+ panic("Flask: Unable to load XSM policy"); > >>+ > >>+ if ( ret ) > >>+ printk("Flask: Starting with no policy loaded.\n"); > >>+ else if ( flask_enforcing ) > >> printk("Flask: Starting in enforcing mode.\n"); > > > >I have a question with regard to XSM in general. > > > >This branching gives me the impression that if no policy is provided > >flask is not enforced even if you have flask_enforned=1. What mode is it > >in? Enforcing or permissive? Is it in permissive mode until a policy is > >loaded? Is it enforcing dummy policy (though it appears to pass every > >check)? > > > >Wei. > > When no policy is loaded, the FLASK policy is equivalent to an allow-all > policy; see xen/xsm/flask/ss/services.c:security_compute_av where it > bails out if !ss_initialized. It could be considered as either enforcing > or being permissive with an allow-all policy, but the actual access is > the same. > > When a policy is loaded later, the value of flask_enforcing will be used > to decide if the policy is applied in enforcing or permissive mode; by > that time, the value could also have been changed using xl setenforce. > Thanks for the explanation. > I decided to make the messages exclusive so that you could more easily > tell by looking at a single line if the policy was loaded and enforced > correctly. Combining both pieces of information in a single line like > the following would also work, if you think this would be better: > > printk("Flask: Starting with%s policy loaded in %s mode.\n", > ret ? " no" : "", flask_enforcing ? "enforcing" : "permissive"); > Yes, I think this is clearer. Thanks. Wei. > -- > Daniel De Graaf > National Security Agency