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>

diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index d513a059cd09ae950eb249b0f057c52934a3afef..94f9e468e07048840c69eb25a2d28e8ddcad5ee5 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;