From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [PATCH 18/23] libxc: Add range checking to
	xc_dom_binloader
Date: Fri, 14 Jun 2013 16:19:04 +0100
Message-ID: <51BB3468.6060004@eu.citrix.com>
References: <1371147302-20767-1-git-send-email-ian.jackson@eu.citrix.com>
	<1371147302-20767-19-git-send-email-ian.jackson@eu.citrix.com>
	<CAFLBxZY-6wzh5wiEFDdOXwxvQ-iO7GD-mCw-mH=o8QgVwpq87A@mail.gmail.com>
	<20923.12455.79753.831636@mariner.uk.xensource.com>
	<51BB321B.80800@eu.citrix.com>
	<CAFLBxZYUU3qL_sS5qiM3KvTmJSuPSay7a18W=g9v3nCYJx7xPg@mail.gmail.com>
	<20923.13137.527678.760500@mariner.uk.xensource.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <20923.13137.527678.760500@mariner.uk.xensource.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, mattjd@gmail.com, security@xen.org
List-Id: xen-devel@lists.xenproject.org

On 14/06/13 16:14, Ian Jackson wrote:
> George Dunlap writes ("Re: [Xen-devel] [PATCH 18/23] libxc: Add range checking to xc_dom_binloader"):
>> if ( dom->kernel-size - sizeof(*table) > 8192)
>>    ptr_end = dom->kernel_blob + 8192
>> else
>>    ptr_end = dom->kernel_size - sizeof(*table);
>>
>> Or something along those lines?
> Yes, I said something similar to Chuck.  Except that your code has a
> bug if kernel_size < sizeof(*table) :-).

...no, because that's already checked by the previous hunk of your 
patch. :-)

> TBH I think I'd rather not disturb this any more than necessary.

I think disturbing it in a way that is obviously correct is better than 
disturbing it in a way that looks redundant.

But I do think that the code in the patch you have, while unnecessarily 
confusing and likely to trip someone up down the road, will do what the 
patch claims it will do.

  -George