drm/atomic: Verify connector->funcs != NULL when clearing states

Unfortunately since we don't have Dave's connector refcounting patch
here yet, it's very possible that drm_atomic_state_default_clear() could
get called by intel_display_resume() when
intel_dp_mst_destroy_connector() isn't completely finished destroying an
mst connector, but has already finished setting connector->funcs to
NULL. As such, we need to treat the connector like it's already been
destroyed and just skip it, otherwise we'll end up dereferencing a NULL
pointer.

This fix is only required for 4.6 and below. David Airlie's patchseries
for 4.7 to add connector reference counting provides a more proper fix
for this.

Changes since v1:
 - Fix leftover whitespace

Upstream fix: 0552f7651bc2 ("drm/i915/mst: use reference counted
connectors. (v3)")
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Lyude <cpaul@redhat.com>

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index aeee083c7f95064fed6c6b08cd67b58d174204af..aed2e3f8a1a280669ea029a10f09412895151be8 100644 (file)
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -150,7 +150,7 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state)
        for (i = 0; i < state->num_connector; i++) {
                struct drm_connector *connector = state->connectors[i];
 
-               if (!connector)
+               if (!connector || !connector->funcs)
                        continue;
 
                /*