netfilter: accommodate different kconfig in nf_set_hooks_head

When CONFIG_NETFILTER_INGRESS is unset (or no), we need to handle
the request for registration properly by dropping the hook.  This
releases the entry during the set.

Fixes: e3b37f1 ("netfilter: replace list_head with single linked list")
Signed-off-by: Aaron Conole <aconole@bytheb.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/core.c

@@ -90,10 +90,12 @@ static void nf_set_hooks_head(struct net *net, const struct nf_hook_ops *reg,
 {
 	switch (reg->pf) {
 	case NFPROTO_NETDEV:
+#ifdef CONFIG_NETFILTER_INGRESS
 		/* We already checked in nf_register_net_hook() that this is
 		 * used from ingress.
 		 */
 		rcu_assign_pointer(reg->dev->nf_hooks_ingress, entry);
+#endif
 		break;
 	default:
 		rcu_assign_pointer(net->nf.hooks[reg->pf][reg->hooknum],
@@ -107,10 +109,15 @@ int nf_register_net_hook(struct net *net, const struct nf_hook_ops *reg)
 	struct nf_hook_entry *hooks_entry;
 	struct nf_hook_entry *entry;
 
-	if (reg->pf == NFPROTO_NETDEV &&
-	    (reg->hooknum != NF_NETDEV_INGRESS ||
-	     !reg->dev || dev_net(reg->dev) != net))
-		return -EINVAL;
+	if (reg->pf == NFPROTO_NETDEV) {
+#ifndef CONFIG_NETFILTER_INGRESS
+		if (reg->hooknum == NF_NETDEV_INGRESS)
+			return -EOPNOTSUPP;
+#endif
+		if (reg->hooknum != NF_NETDEV_INGRESS ||
+		    !reg->dev || dev_net(reg->dev) != net)
+			return -EINVAL;
+	}
 
 	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 	if (!entry)