This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


[Xen-devel] Re: [PATCH] [ACM/Xen] Fix policy buffer layout changed with

To: "George S. Coker, II" <gscoker@xxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] [ACM/Xen] Fix policy buffer layout changed with XSM
From: Stefan Berger <stefanb@xxxxxxxxxx>
Date: Tue, 4 Sep 2007 14:37:51 -0400
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir@xxxxxxxxxxxxx>
Delivery-date: Wed, 05 Sep 2007 08:09:43 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <1188930550.4372.250.camel@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

"George S. Coker, II" <gscoker@xxxxxxxxxxxxxx> wrote on 09/04/2007 02:29:10 PM:

> On Tue, 2007-09-04 at 10:57 -0400, Stefan Berger wrote:
> > This fixes a regression due to changes in the policy buffer layout
> > submitted by the XSM module.
> >
> Hi Stefan,
> This was done to make the ACM magic number the first word in the policy
> file.  This seemed to be the logical choice to afford ACM the greatest
> flexibility for loading policies under XSM.  In principal, under XSM, a
> security module could be capable of loading and parsing policies over a
> range of policy versions.

Did you adapt the tools to generate a binary policy in that form?

> Your patch reverts the ACM module to the original form where the first
> word of the policy file is the policy version - which could change over
> time.  This is the general problem of magic numbers.

Yes, I changed it back because it was broken, at least it did not accept the policy I tried to load.


> A benefit of your patch is old ACM policies will not need to be
> recompiled to work under XSM with this patch, but I see there being
> future confusion and a potential loss of flexibility for ACM by making
> this change.  I would argue that the ACM policy version should instead
> be bumped for the move to XSM since the XSM patches actually caused a
> format change to the ACM policy binary.
> Admittedly, this discussion is moot because ACM has only one policy
> version at this time.  The XSM_MAGIC number must also be updated to
> 03000000 to ensure proper boot time policy detection under XSM with your
> patch.
> I also see that there are dups of /xsm in the includes dir.  Since this
> was a restructuring from inclusion in xen-staging, perhaps some cleanups
> are in order.  Keir?
> George
Xen-devel mailing list