Re: [Xen-devel] [PATCH] xen: add gntdev

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

On Tue, Dec 04, 2012 at 03:07:39PM -0500, Thor Lancelot Simon wrote:
> On Tue, Dec 04, 2012 at 04:26:19PM +0100, Roger Pau Monn? wrote:
> > 
> > Independently of what we end up doing as default for handling raw file
> > disks, could someone review this code?
> > 
> > It's the first time I've done a device, so someone with more experience
> > should review it.
> 
> I am not sure I entirely follow what this code's doing, but it seems to
> me it may allow arbitrary physical pages to be exposed to userspace
> processes in dom0 -- or in a domU, albeit only if dom0 userspace says so.
> 
> Is that a correct understanding of one of its effects?  If so, there's
> a problem, since not being able to do precisely that is one important
> assumption of the 4.4BSD security model.

If I read it properly, It allows only to map pages that are part of a
grant. You provide the ioctl a grant reference, and this is what
the driver uses to find the physical pages. So it should be limited to
pages that are referenced by a grant.

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--

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