drm: Check crtc x and y coordinates

commit 1d97e915 upstream.

The crtc x/y panning coordinates are stored as signed integers
internally. The user provides them as unsigned, so we should check
that the user provided values actually fit in the internal datatypes.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/drm_crtc.c

@@ -1505,6 +1505,10 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return -EINVAL;
 
+	/* For some reason crtc x/y offsets are signed internally. */
+	if (crtc_req->x > INT_MAX || crtc_req->y > INT_MAX)
+		return -ERANGE;
+
 	mutex_lock(&dev->mode_config.mutex);
 	obj = drm_mode_object_find(dev, crtc_req->crtc_id,
 				   DRM_MODE_OBJECT_CRTC);