tun: call dev_get_valid_name() before register_netdevice()

register_netdevice() could fail early when we have an invalid
dev name, in which case ->ndo_uninit() is not called. For tun
device, this is a problem because a timer etc. are already
initialized and it expects ->ndo_uninit() to clean them up.

We could move these initializations into a ->ndo_init() so
that register_netdevice() knows better, however this is still
complicated due to the logic in tun_detach().

Therefore, I choose to just call dev_get_valid_name() before
register_netdevice(), which is quicker and much easier to audit.
And for this specific case, it is already enough.

Fixes: 96442e42429e ("tuntap: choose the txq based on rxq")
Reported-by: Dmitry Alexeev <avekceeb@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int __netdev_adjacent_dev_insert(struct net_device *dev,
					struct net_device *adj_dev,
					struct list_head *dev_list,
					void *private, bool master)
{
	struct netdev_adjacent *adj;
	int ret;

	adj = __netdev_find_adj(adj_dev, dev_list);

	if (adj) {
		adj->ref_nr += 1;
		pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d\n",
			 dev->name, adj_dev->name, adj->ref_nr);

		return 0;
	}

	adj = kmalloc(sizeof(*adj), GFP_KERNEL);
	if (!adj)
		return -ENOMEM;

	adj->dev = adj_dev;
	adj->master = master;
	adj->ref_nr = 1;
	adj->private = private;
	dev_hold(adj_dev);

	pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d; dev_hold on %s\n",
		 dev->name, adj_dev->name, adj->ref_nr, adj_dev->name);

	if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list)) {
		ret = netdev_adjacent_sysfs_add(dev, adj_dev, dev_list);
		if (ret)
			goto free_adj;
	}

	/* Ensure that master link is always the first item in list. */
	if (master) {
		ret = sysfs_create_link(&(dev->dev.kobj),
					&(adj_dev->dev.kobj), "master");
		if (ret)
			goto remove_symlinks;

		list_add_rcu(&adj->list, dev_list);
	} else {
		list_add_tail_rcu(&adj->list, dev_list);
	}

	return 0;

remove_symlinks:
	if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list))
		netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);
free_adj:
	kfree(adj);
	dev_put(adj_dev);

	return ret;
}

static int __netdev_adjacent_dev_insert(struct net_device *dev,
					struct net_device *adj_dev,
					struct list_head *dev_list,
					void *private, bool master)
{
	struct netdev_adjacent *adj;
	int ret;

	adj = __netdev_find_adj(adj_dev, dev_list);

	if (adj) {
		adj->ref_nr += 1;
		pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d\n",
			 dev->name, adj_dev->name, adj->ref_nr);

		return 0;
	}

	adj = kmalloc(sizeof(*adj), GFP_KERNEL);
	if (!adj)
		return -ENOMEM;

	adj->dev = adj_dev;
	adj->master = master;
	adj->ref_nr = 1;
	adj->private = private;
	dev_hold(adj_dev);

	pr_debug("Insert adjacency: dev %s adj_dev %s adj->ref_nr %d; dev_hold on %s\n",
		 dev->name, adj_dev->name, adj->ref_nr, adj_dev->name);

	if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list)) {
		ret = netdev_adjacent_sysfs_add(dev, adj_dev, dev_list);
		if (ret)
			goto free_adj;
	}

	/* Ensure that master link is always the first item in list. */
	if (master) {
		ret = sysfs_create_link(&(dev->dev.kobj),
					&(adj_dev->dev.kobj), "master");
		if (ret)
			goto remove_symlinks;

		list_add_rcu(&adj->list, dev_list);
	} else {
		list_add_tail_rcu(&adj->list, dev_list);
	}

	return 0;

remove_symlinks:
	if (netdev_adjacent_is_neigh_list(dev, adj_dev, dev_list))
		netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);
free_adj:
	kfree(adj);
	dev_put(adj_dev);

	return ret;
}
