Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/net/ipv4/udp_diag.c b/net/ipv4/udp_diag.c
index d9ad986..910555a 100644
--- a/net/ipv4/udp_diag.c
+++ b/net/ipv4/udp_diag.c
@@ -1,12 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * udp_diag.c	Module for monitoring UDP transport protocols sockets.
  *
  * Authors:	Pavel Emelyanov, <xemul@parallels.com>
- *
- *	This program is free software; you can redistribute it and/or
- *      modify it under the terms of the GNU General Public License
- *      as published by the Free Software Foundation; either version
- *      2 of the License, or (at your option) any later version.
  */
 
 
@@ -42,6 +38,7 @@
 
 	rcu_read_lock();
 	if (req->sdiag_family == AF_INET)
+		/* src and dst are swapped for historical reasons */
 		sk = __udp4_lib_lookup(net,
 				req->id.idiag_src[0], req->id.idiag_sport,
 				req->id.idiag_dst[0], req->id.idiag_dport,