linux-kernel - Re: DRM security flaws and security levels.

Open Source and information security mailing list archives

Date:	Fri, 11 Apr 2014 23:15:15 +0200
From:	Thomas Hellstrom <thellstrom@...are.com>
To:	David Herrmann <dh.herrmann@...il.com>
CC:	Thomas Hellstrom <thellstrom@...are.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: DRM security flaws and security levels.

On 04/11/2014 10:31 PM, David Herrmann wrote:
> Hi
>
> On Fri, Apr 11, 2014 at 2:42 PM, Thomas Hellstrom <thellstrom@...are.com> wrote:
>> as was discussed a while ago, there are some serious security flaws with
>> the current drm master model, that allows a
>> user that had previous access or current access to an X server terminal
>> to access the GPU memory of the active X server, without being
>> authenticated to the X server and thereby also access other user's
>> secret information
> 1a) and 1b) are moot if you disallow primary-node access but require
> clients to use render-nodes with dma-buf. There're no gem-names on
> render-nodes so no way to access other buffers (assuming the GPU does
> command-stream checking and/or VM).

Disallowing primary node access will break older user-space drivers and
non-root
EGL clients. I'm not sure that's OK, even if the change is done from
user-space.
A simple gem fix would also do the trick.

>
> 2) There is no DRM-generic data other than buffers that is global. So
> imho this is a driver-specific issue.
>
> So I cannot see why this is a DRM issue. The only leaks I see are
> legacy interfaces and driver-specific interfaces. The first can be
> disabled via chmod() for clients, and the second is something driver
> authors should fix.

Yeah, but some driver authors can't or won't fix the drivers w r t this,
hence the security levels.

Thanks,
/Thomas

>
> Thanks
> David
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> dri-devel@...ts.freedesktop.org
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