Re: [RFC] macvlan: add tap device backend

Arnd Bergmann wrote:

+static int macvtap_newlink(struct net *src_net,
+			   struct net_device *dev,
+			   struct nlattr *tb[],
+			   struct nlattr *data[])
+{
+	struct device *classdev;
+	dev_t devt;
+	int err;
+
+	err = macvlan_common_newlink(src_net, dev, tb, data,
+				     macvtap_receive, macvtap_forward);
+	if (err)
+		goto out;
+
+	devt = MKDEV(MAJOR(macvtap_major), dev->ifindex);
+
+	classdev = device_create(macvtap_class, &dev->dev, devt,
+				 dev, "tap%d", dev->ifindex);
+	if (IS_ERR(classdev)) {
+		err = PTR_ERR(classdev);
+		macvtap_del_queues(dev);
+		macvlan_dellink(dev, NULL);

I think this may cause a double free since macvlan_dellink() will
free the device and rtnl_newlink() will free it again on error.

+	}
+
+out:
+	return err;
+}
+
+static void macvtap_dellink(struct net_device *dev,
+			    struct list_head *head)
+{
+	device_destroy(macvtap_class,
+		       MKDEV(MAJOR(macvtap_major), dev->ifindex));
+
+	macvtap_del_queues(dev);
+	macvlan_dellink(dev, head);
+}
+
+static struct rtnl_link_ops macvtap_link_ops __read_mostly = {
+	.kind		= "macvtap",
+	.newlink	= macvtap_newlink,
+	.dellink	= macvtap_dellink,
+};