[Intel-gfx] [PATCH] drm/i915/fbdev: Check for existence of ifbdev->vma before operations

[Tvrtko Ursulin]

On 04/07/2017 11:06, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2017-07-04 10:59:29)
>>
>> On 22/06/2017 17:02, Chris Wilson wrote:
>>> Commit fabef825626d ("drm/i915: Drop struct_mutex around frontbuffer
>>> flushes") adds a dependency to ifbdev->vma when flushing the framebufer,
>>> but the checks are only against the existence of the ifbdev->fb and not
>>> against ifbdev->vma. This leaves a window of opportunity where we may
>>> try to operate on the fbdev prior to it being probed (thanks to
>>> asynchronous booting).
>>
>> How about changing the intelfb_alloc to not write the fb to ifbdev but
>> instead return it to the caller, so intelfb_create could then set the
>> ifbdev->fb and ifbdev->vma atomically under the mutex?
> 
> Midlayer mishap.

After an IRC chat I see that the issue is intel_fbdev_init_bios also 
sets the fb and not vma, which I missed earlier.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko