Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/net/l3mdev/l3mdev.c b/net/l3mdev/l3mdev.c
index 8da86ce..f35899d 100644
--- a/net/l3mdev/l3mdev.c
+++ b/net/l3mdev/l3mdev.c
@@ -1,12 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * net/l3mdev/l3mdev.c - L3 master device implementation
  * Copyright (c) 2015 Cumulus Networks
  * Copyright (c) 2015 David Ahern <dsa@cumulusnetworks.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.
  */
 
 #include <linux/netdevice.h>
@@ -47,6 +43,24 @@
 EXPORT_SYMBOL_GPL(l3mdev_master_ifindex_rcu);
 
 /**
+ *	l3mdev_master_upper_ifindex_by_index - get index of upper l3 master
+ *					       device
+ *	@net: network namespace for device index lookup
+ *	@ifindex: targeted interface
+ */
+int l3mdev_master_upper_ifindex_by_index_rcu(struct net *net, int ifindex)
+{
+	struct net_device *dev;
+
+	dev = dev_get_by_index_rcu(net, ifindex);
+	while (dev && !netif_is_l3_master(dev))
+		dev = netdev_master_upper_dev_get(dev);
+
+	return dev ? dev->ifindex : 0;
+}
+EXPORT_SYMBOL_GPL(l3mdev_master_upper_ifindex_by_index_rcu);
+
+/**
  *	l3mdev_fib_table - get FIB table id associated with an L3
  *                             master interface
  *	@dev: targeted interface
@@ -104,6 +118,8 @@
  *			     local and multicast addresses
  *	@net: network namespace for device index lookup
  *	@fl6: IPv6 flow struct for lookup
+ *	This function does not hold refcnt on the returned dst.
+ *	Caller must hold rcu_read_lock().
  */
 
 struct dst_entry *l3mdev_link_scope_lookup(struct net *net,
@@ -112,9 +128,8 @@
 	struct dst_entry *dst = NULL;
 	struct net_device *dev;
 
+	WARN_ON_ONCE(!rcu_read_lock_held());
 	if (fl6->flowi6_oif) {
-		rcu_read_lock();
-
 		dev = dev_get_by_index_rcu(net, fl6->flowi6_oif);
 		if (dev && netif_is_l3_slave(dev))
 			dev = netdev_master_upper_dev_get_rcu(dev);
@@ -122,8 +137,6 @@
 		if (dev && netif_is_l3_master(dev) &&
 		    dev->l3mdev_ops->l3mdev_link_scope_lookup)
 			dst = dev->l3mdev_ops->l3mdev_link_scope_lookup(dev, fl6);
-
-		rcu_read_unlock();
 	}
 
 	return dst;