netfilter: nf_tables: imbalance in flowtable binding

All these cases cause imbalance between BIND and UNBIND calls:

- Delete an interface from a flowtable with multiple interfaces

- Add a (device to a) flowtable with --check flag

- Delete a netns containing a flowtable

- In an interactive nft session, create a table with owner flag and
  flowtable inside, then quit.

Fix it by calling FLOW_BLOCK_UNBIND when unregistering hooks, then
remove late FLOW_BLOCK_UNBIND call when destroying flowtable.

Fixes: ff4bf2f ("netfilter: nf_tables: add nft_unregister_flowtable_hook()")
Reported-by: Phil Sutter <phil@nwl.cc>
Tested-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -8822,13 +8822,16 @@ static void nft_unregister_flowtable_hook(struct net *net,
 }
 
 static void __nft_unregister_flowtable_net_hooks(struct net *net,
+						 struct nft_flowtable *flowtable,
 						 struct list_head *hook_list,
 					         bool release_netdev)
 {
 	struct nft_hook *hook, *next;
 
 	list_for_each_entry_safe(hook, next, hook_list, list) {
 		nf_unregister_net_hook(net, &hook->ops);
+		flowtable->data.type->setup(&flowtable->data, hook->ops.dev,
+					    FLOW_BLOCK_UNBIND);
 		if (release_netdev) {
 			list_del(&hook->list);
 			kfree_rcu(hook, rcu);
@@ -8837,9 +8840,10 @@ static void __nft_unregister_flowtable_net_hooks(struct net *net,
 }
 
 static void nft_unregister_flowtable_net_hooks(struct net *net,
+					       struct nft_flowtable *flowtable,
 					       struct list_head *hook_list)
 {
-	__nft_unregister_flowtable_net_hooks(net, hook_list, false);
+	__nft_unregister_flowtable_net_hooks(net, flowtable, hook_list, false);
 }
 
 static int nft_register_flowtable_net_hooks(struct net *net,
@@ -9481,8 +9485,6 @@ static void nf_tables_flowtable_destroy(struct nft_flowtable *flowtable)
 
 	flowtable->data.type->free(&flowtable->data);
 	list_for_each_entry_safe(hook, next, &flowtable->hook_list, list) {
-		flowtable->data.type->setup(&flowtable->data, hook->ops.dev,
-					    FLOW_BLOCK_UNBIND);
 		list_del_rcu(&hook->list);
 		kfree_rcu(hook, rcu);
 	}
@@ -10870,6 +10872,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 							   &nft_trans_flowtable_hooks(trans),
 							   trans->msg_type);
 				nft_unregister_flowtable_net_hooks(net,
+								   nft_trans_flowtable(trans),
 								   &nft_trans_flowtable_hooks(trans));
 			} else {
 				list_del_rcu(&nft_trans_flowtable(trans)->list);
@@ -10878,6 +10881,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 							   NULL,
 							   trans->msg_type);
 				nft_unregister_flowtable_net_hooks(net,
+						nft_trans_flowtable(trans),
 						&nft_trans_flowtable(trans)->hook_list);
 			}
 			break;
@@ -11140,11 +11144,13 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
 		case NFT_MSG_NEWFLOWTABLE:
 			if (nft_trans_flowtable_update(trans)) {
 				nft_unregister_flowtable_net_hooks(net,
+						nft_trans_flowtable(trans),
 						&nft_trans_flowtable_hooks(trans));
 			} else {
 				nft_use_dec_restore(&table->use);
 				list_del_rcu(&nft_trans_flowtable(trans)->list);
 				nft_unregister_flowtable_net_hooks(net,
+						nft_trans_flowtable(trans),
 						&nft_trans_flowtable(trans)->hook_list);
 			}
 			break;
@@ -11737,7 +11743,8 @@ static void __nft_release_hook(struct net *net, struct nft_table *table)
 	list_for_each_entry(chain, &table->chains, list)
 		__nf_tables_unregister_hook(net, table, chain, true);
 	list_for_each_entry(flowtable, &table->flowtables, list)
-		__nft_unregister_flowtable_net_hooks(net, &flowtable->hook_list,
+		__nft_unregister_flowtable_net_hooks(net, flowtable,
+						     &flowtable->hook_list,
 						     true);
 }