[Libva] [PATCH] drm: improve check for authentication.

[Daniel Vetter]

On Tue, Jul 16, 2013 at 2:38 PM, Gwenole Beauchesne <gb.devel at gmail.com> wrote:
>
> 2013/7/16 Daniel Vetter <daniel at ffwll.ch>:
>> On Mon, Jul 15, 2013 at 6:30 PM, Gwenole Beauchesne <gb.devel at gmail.com> wrote:
>
>>> On Linux systems, the drmGetClient() function would return the thread ID
>>> instead of the actual process ID.
>>>
>>> Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne at intel.com>
>>
>> Oh dear, why is it always libva. I've prepared a patch to kill this
>> ioctl (almost) completely since it's imo rather pointless. Now I've
>> just discovered that libva uses it and will make it much harder to
>> fake things in the kernel! Or have I just misread the code and it's
>> actually possible to return -EINVAL for this ioctl and libva will
>> transparently fall back to doing the X11 auth stuff?
>
> Yes, we will transparently fallback to X11 auth. In this case, we
> should not check auth status again if X11 auth was successful.

Re-reading the code you recheck the auth status even if
va_drm_authenticate succeeded, so I think completely breaking the
GET_CLIENT ioctl won't work out.

> However, drmGetClient() was used to check we are already
> authenticated. What would the alternative be?

I've just wondered a bit why libva can't keep track of the auth status
like mesa and only attempt the auth dance once. So imo userspace
doesn't really need to know this information. Anyway it'll all die
with the advent of rendernodes, the only downside is that it'll make
transparently using rendernodes instead of of the legacy nodes for drm
clients a bit more awkward ...
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch