netfilter: nf_tables: skip set commit for deleted/destroyed sets

NFT_MSG_DELSET deactivates all elements in the set, skip
set->ops->commit() to avoid the unnecessary clone (for the pipapo case)
as well as the sync GC cycle, which could deactivate again expired
elements in such set.

Fixes: 5f68718b ("netfilter: nf_tables: GC transaction API to avoid race with control plane")
Reported-by: Kevin Rich <kevinrich1337@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -9887,7 +9887,7 @@ static void nft_set_commit_update(struct list_head *set_update_list)
 	list_for_each_entry_safe(set, next, set_update_list, pending_update) {
 		list_del_init(&set->pending_update);
 
-		if (!set->ops->commit)
+		if (!set->ops->commit || set->dead)
 			continue;
 
 		set->ops->commit(set);