From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Thu, 1 Feb 2018 18:49:00 +0100
Subject: [PATCH] netfilter: nft_flow_offload: wait for garbage collector
 to run after cleanup

If netdevice goes down, then flowtable entries are scheduled to be
removed. Wait for garbage collector to have a chance to run so it can
delete them from the hashtable.

The flush call might sleep, so hold the nfnl mutex from
nft_flow_table_iterate() instead of rcu read side lock. The use of the
nfnl mutex is also implicitly fixing races between updates via nfnetlink
and netdevice event.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4919,13 +4919,13 @@ void nft_flow_table_iterate(struct net *
 	struct nft_flowtable *flowtable;
 	const struct nft_table *table;
 
-	rcu_read_lock();
-	list_for_each_entry_rcu(table, &net->nft.tables, list) {
-		list_for_each_entry_rcu(flowtable, &table->flowtables, list) {
+	nfnl_lock(NFNL_SUBSYS_NFTABLES);
+	list_for_each_entry(table, &net->nft.tables, list) {
+		list_for_each_entry(flowtable, &table->flowtables, list) {
 			iter(&flowtable->data, data);
 		}
 	}
-	rcu_read_unlock();
+	nfnl_unlock(NFNL_SUBSYS_NFTABLES);
 }
 EXPORT_SYMBOL_GPL(nft_flow_table_iterate);
 
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -208,6 +208,7 @@ static void nft_flow_offload_iterate_cle
 					     void *data)
 {
 	nf_flow_table_iterate(flowtable, flow_offload_iterate_cleanup, data);
+	flush_delayed_work(&flowtable->gc_work);
 }
 
 static int flow_offload_netdev_event(struct notifier_block *this,
