util-net: Make sure that there is real data in message

Otherwise weird address might be dereferenced.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>

util-net.c

@@ -57,7 +57,7 @@ int recv_fd(int sock)
 		return ret;
 
 	cmsg = CMSG_FIRSTHDR(&msg);
-	if (!cmsg->cmsg_type == SCM_RIGHTS)
+	if (!cmsg || !cmsg->cmsg_type == SCM_RIGHTS)
 		return -2;
 
 	cmsg_data = (int *)CMSG_DATA(cmsg);