drm/radeon: check incoming cliprects pointer

commit fefaedcf upstream.

The "boxes" parameter points into userspace memory. It should be verified
like any other operation against user memory.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/radeon/r300_cmdbuf.c

@@ -74,7 +74,7 @@ static int r300_emit_cliprects(drm_radeon_private_t *dev_priv,
 		OUT_RING(CP_PACKET0(R300_RE_CLIPRECT_TL_0, nr * 2 - 1));
 
 		for (i = 0; i < nr; ++i) {
-			if (DRM_COPY_FROM_USER_UNCHECKED
+			if (DRM_COPY_FROM_USER
 			    (&box, &cmdbuf->boxes[n + i], sizeof(box))) {
 				DRM_ERROR("copy cliprect faulted\n");
 				return -EFAULT;