net: don't try to ops lock uninitialized devs

We need to be careful when operating on dev while in rtnl_create_link().
Some devices (vxlan) initialize netdev_ops in ->newlink, so later on.
Avoid using netdev_lock_ops(), the device isn't registered so we
cannot legally call its ops or generate any notifications for it.

netdev_ops_assert_locked_or_invisible() is safe to use, it checks
registration status first.

Reported-by: syzbot+de1c7d68a10e3f123bdd@syzkaller.appspotmail.com
Fixes: 04efcee ("net: hold instance lock during NETDEV_CHANGE")
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250415151552.768373-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -1520,6 +1520,8 @@ EXPORT_SYMBOL(netdev_features_change);
 
 void netif_state_change(struct net_device *dev)
 {
+	netdev_ops_assert_locked_or_invisible(dev);
+
 	if (dev->flags & IFF_UP) {
 		struct netdev_notifier_change_info change_info = {
 			.info.dev = dev,

net/core/rtnetlink.c

@@ -3676,11 +3676,8 @@ struct net_device *rtnl_create_link(struct net *net, const char *ifname,
 				nla_len(tb[IFLA_BROADCAST]));
 	if (tb[IFLA_TXQLEN])
 		dev->tx_queue_len = nla_get_u32(tb[IFLA_TXQLEN]);
-	if (tb[IFLA_OPERSTATE]) {
-		netdev_lock_ops(dev);
+	if (tb[IFLA_OPERSTATE])
 		set_operstate(dev, nla_get_u8(tb[IFLA_OPERSTATE]));
-		netdev_unlock_ops(dev);
-	}
 	if (tb[IFLA_LINKMODE])
 		dev->link_mode = nla_get_u8(tb[IFLA_LINKMODE]);
 	if (tb[IFLA_GROUP])