net: vlan: avoid leaks on register_vlan_dev() failures

VLAN checks for NETREG_UNINITIALIZED to distinguish between
registration failure and unregistration in progress.

Since commit cb626bf566 ("net-sysfs: Fix reference count leak")
registration failure may, however, result in NETREG_UNREGISTERED
as well as NETREG_UNINITIALIZED.

This fix is similer to cebb69754f ("rtnetlink: Fix
memory(net_device) leak when ->newlink fails")

Fixes: cb626bf566 ("net-sysfs: Fix reference count leak")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan.c

@@ -284,7 +284,8 @@ static int register_vlan_device(struct net_device *real_dev, u16 vlan_id)
 	return 0;
 
 out_free_newdev:
-	if (new_dev->reg_state == NETREG_UNINITIALIZED)
+	if (new_dev->reg_state == NETREG_UNINITIALIZED ||
+	    new_dev->reg_state == NETREG_UNREGISTERED)
 		free_netdev(new_dev);
 	return err;
 }