drm/i915: Fix oops in overlay due to frontbuffer tracking

The vma will be NULL if the overlay was previously off, so
dereferencing it will oops. Check for NULL before doing that.

Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Fixes: 9b3b7841b86d ("drm/i915/overlay: Use VMA as the primary tracker for images")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-2-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
(cherry picked from commit 4a15cdbbc55463e55a7cdcf33f84ccc742ca9c29)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index 57ef9c88843cbfd3c8e9c9a37c65a952057cd08d..e589e17876dc134b60bbb5958ad1fe856f2f118e 100644 (file)
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -840,8 +840,8 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
        if (ret)
                goto out_unpin;
 
-       i915_gem_track_fb(overlay->vma->obj, new_bo,
-                         INTEL_FRONTBUFFER_OVERLAY(pipe));
+       i915_gem_track_fb(overlay->vma ? overlay->vma->obj : NULL,
+                         vma->obj, INTEL_FRONTBUFFER_OVERLAY(pipe));
 
        overlay->old_vma = overlay->vma;
        overlay->vma = vma;