ipv6: Hold rtnl_net_lock() in addrconf_init() and addrconf_cleanup().

addrconf_init() holds RTNL for blackhole_netdev, which is the global
device in init_net.

addrconf_cleanup() holds RTNL to clean up devices in init_net too.

Let's use rtnl_net_lock(&init_net) there.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115080608.28127-6-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: q2ven

net/ipv6/addrconf.c

@@ -7460,9 +7460,9 @@ int __init addrconf_init(void)
 		goto out_nowq;
 	}
 
-	rtnl_lock();
+	rtnl_net_lock(&init_net);
 	idev = ipv6_add_dev(blackhole_netdev);
-	rtnl_unlock();
+	rtnl_net_unlock(&init_net);
 	if (IS_ERR(idev)) {
 		err = PTR_ERR(idev);
 		goto errlo;
@@ -7512,17 +7512,17 @@ void addrconf_cleanup(void)
 
 	rtnl_af_unregister(&inet6_ops);
 
-	rtnl_lock();
+	rtnl_net_lock(&init_net);
 
 	/* clean dev list */
 	for_each_netdev(&init_net, dev) {
-		if (__in6_dev_get(dev) == NULL)
+		if (!__in6_dev_get_rtnl_net(dev))
 			continue;
 		addrconf_ifdown(dev, true);
 	}
 	addrconf_ifdown(init_net.loopback_dev, true);
 
-	rtnl_unlock();
+	rtnl_net_unlock(&init_net);
 
 	destroy_workqueue(addrconf_wq);
 }