net: fix sysfs permssions when device changes network namespace

Now that we moved all the helpers in place and make use netdev_change_owner()
to fixup the permissions when moving network devices between network
namespaces.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -10003,6 +10003,7 @@ EXPORT_SYMBOL(unregister_netdev);
 
 int dev_change_net_namespace(struct net_device *dev, struct net *net, const char *pat)
 {
+	struct net *net_old = dev_net(dev);
 	int err, new_nsid, new_ifindex;
 
 	ASSERT_RTNL();
@@ -10018,7 +10019,7 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 
 	/* Get out if there is nothing todo */
 	err = 0;
-	if (net_eq(dev_net(dev), net))
+	if (net_eq(net_old, net))
 		goto out;
 
 	/* Pick the destination device name, and ensure
@@ -10094,6 +10095,12 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 	err = device_rename(&dev->dev, dev->name);
 	WARN_ON(err);
 
+	/* Adapt owner in case owning user namespace of target network
+	 * namespace is different from the original one.
+	 */
+	err = netdev_change_owner(dev, net_old, net);
+	WARN_ON(err);
+
 	/* Add the device back in the hashes */
 	list_netdevice(dev);