vlan: fail early when creating netdev named config

Similarly, vlan will create  /proc/net/vlan/<dev>, so when we
create dev with name "config", it will confict with
/proc/net/vlan/config.

Reported-by: Stephane Chazelas <stephane.chazelas@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlanproc.c b/net/8021q/vlanproc.c
index 1d0e8921..ae63cf7 100644
--- a/net/8021q/vlanproc.c
+++ b/net/8021q/vlanproc.c
@@ -171,6 +171,8 @@
 	struct vlan_dev_priv *vlan = vlan_dev_priv(vlandev);
 	struct vlan_net *vn = net_generic(dev_net(vlandev), vlan_net_id);
 
+	if (!strcmp(vlandev->name, name_conf))
+		return -EINVAL;
 	vlan->dent =
 		proc_create_data(vlandev->name, S_IFREG|S_IRUSR|S_IWUSR,
 				 vn->proc_vlan_dir, &vlandev_fops, vlandev);