[PATCH] drm/vmwgfx: Add some checks to vmw_cursor_plane_atomic_update

[Maaz Mombasawala <maaz.mombasawala@broadcom.com>]

In cases where old_state may not be present we hit a null dereference.
Add a check to fix this and also do an early return if there is no
new_state or crtc since there is nothing to do in that case.
This fixes igt test kms_cursor_legacy@torture-bo.

Signed-off-by: Maaz Mombasawala <maaz.mombasawala@broadcom.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c b/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c
index c46f17ba7236..88b7185a8371 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c
@@ -744,9 +744,14 @@ vmw_cursor_plane_atomic_update(struct drm_plane *plane,
 	struct vmw_bo *bo;
 	struct drm_plane_state *new_state =
 		drm_atomic_get_new_plane_state(state, plane);
+	if (!new_state)
+		return;
 	struct drm_plane_state *old_state =
 		drm_atomic_get_old_plane_state(state, plane);
-	struct drm_crtc *crtc = new_state->crtc ?: old_state->crtc;
+	struct drm_crtc *crtc = new_state->crtc ? new_state->crtc :
+		(old_state ? old_state->crtc : NULL);
+	if (!crtc)
+		return;
 	struct vmw_private *dev_priv = vmw_priv(plane->dev);
 	struct vmw_display_unit *du = vmw_crtc_to_du(crtc);
 	struct vmw_plane_state *vps = vmw_plane_state_to_vps(new_state);
-- 
2.53.0