drm/i915: Fix NULL ptr deref by checking new_crtc_state

intel_atomic_get_new_crtc_state can return NULL, unless crtc state wasn't
obtained previously with intel_atomic_get_crtc_state, so we must check it
for NULLness here, just as in many other places, where we can't guarantee
that intel_atomic_get_crtc_state was called.
We are currently getting NULL ptr deref because of that, so this fix was
confirmed to help.

Fixes: 74a75dc90869 ("drm/i915/display: move plane prepare/cleanup to intel_atomic_plane.c")
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230505082212.27089-1-stanislav.lisovskiy@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
index 9f670dc..4125ee0 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
@@ -1029,7 +1029,7 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
        int ret;
 
        if (old_obj) {
-               const struct intel_crtc_state *crtc_state =
+               const struct intel_crtc_state *new_crtc_state =
                        intel_atomic_get_new_crtc_state(state,
                                                        to_intel_crtc(old_plane_state->hw.crtc));
 
@@ -1044,7 +1044,7 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
                 * This should only fail upon a hung GPU, in which case we
                 * can safely continue.
                 */
-               if (intel_crtc_needs_modeset(crtc_state)) {
+               if (new_crtc_state && intel_crtc_needs_modeset(new_crtc_state)) {
                        ret = i915_sw_fence_await_reservation(&state->commit_ready,
                                                              old_obj->base.resv,
                                                              false, 0,