netfilter: nf_tables: fix oops when deleting a chain with references

commit 780f57420cdac84eabec388868678ede19f7d682

Author: Patrick McHardy <[email protected]>
Date:   Fri Jan 24 13:23:52 2014 +0000

netfilter: nf_tables: fix oops when deleting a chain with references

THe following commands trigger an oops:

# nft -i
nft> add table filter
nft> add chain filter input { type filter hook input priority 0; } nft> add chain filter test
nft> add rule filter input jump test
nft> delete chain filter test

We need to check the chain use counter before allowing destruction since we might have references from sets or jump rules.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=69341

index 117bbaa..9ce3053 100644
@@ -1045,7 +1045,7 @@ static int nf_tables_delchain(struct sock *nlsk, struct sk_buff *skb,
 	if (IS_ERR(chain))
 		return PTR_ERR(chain);
 
-	if (!list_empty(&chain->rules))
+	if (!list_empty(&chain->rules) || chain->use > 0)
 		return -EBUSY;
 
 	list_del(&chain->list);

Applied, thanks Patrick.