ipv6: Use RCU in ip6_input()

Instead of grabbing rcu_read_lock() from ip6_input_finish(),
do it earlier in is caller, so that ip6_input() access
to dev_net() can be validated by LOCKDEP.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250205155120.1676781-13-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/ip6_input.c

@@ -477,19 +477,23 @@ void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	skb_clear_delivery_time(skb);
-	rcu_read_lock();
 	ip6_protocol_deliver_rcu(net, skb, 0, false);
-	rcu_read_unlock();
 
 	return 0;
 }
 
 
 int ip6_input(struct sk_buff *skb)
 {
-	return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
-		       dev_net(skb->dev), NULL, skb, skb->dev, NULL,
-		       ip6_input_finish);
+	int res;
+
+	rcu_read_lock();
+	res = NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
+		      dev_net_rcu(skb->dev), NULL, skb, skb->dev, NULL,
+		      ip6_input_finish);
+	rcu_read_unlock();
+
+	return res;
 }
 EXPORT_SYMBOL_GPL(ip6_input);