WARNING - OLD ARCHIVES

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/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] Re: xen crash in tmem: checking a xen pfn for domain ownersh

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: [Xen-devel] Re: xen crash in tmem: checking a xen pfn for domain ownership
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 17 Sep 2010 17:35:04 +0100
Cc: Xen-devel <Xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Fri, 17 Sep 2010 09:35:44 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <5638cf67-e92c-45b3-8806-a0baba1eb8aa@default>
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/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: ActWhe4mQJ3pvMRqRNW7k6nNKyT1WAAAFmjb
Thread-topic: xen crash in tmem: checking a xen pfn for domain ownership
User-agent: Microsoft-Entourage/12.26.0.100708
If you could be doing memory sharing then you might need to use
gfn_to_mfn_unshare()? Otherwise it looks pretty plausible, and that one flaw
is pretty minor as you're probably not using memshr.

 -- Keir

On 17/09/2010 17:29, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> Does the construct:
> 
>   xen_pfn_t gpfn;
>   p2m_type_t t;
>   unsigned long mfn;
> 
>   mfn = mfn_x(gfn_to_mfn(current->domain, gpfn, &t));
>   if (t != p2m_ram_rw || cli_mfn == INVALID_MFN)
>       return NULL; /* bad */
>   return map_domain_page(mfn)
> 
> somehow check to ensure that pfn belongs to current->domain?
> (See cli_mfn_to_va() in common/tmem_xen.c.)
> 
> If not, is there an easy way to perform that check?
> (preferably one that works for both HVM and PV guests)
> 
> In debugging a tmem Linux-side guest patch, I discovered
> that a bad mfn passed by the guest can crash Xen and
> I think this assumption might be the problem.
> 
> Thanks,
> Dan



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel