netfilter: nf_tables: out-of-bound check in chain blob

Add current size of rule expressions to the boundary check.

Fixes: 2c865a8 ("netfilter: nf_tables: add rule blob layout")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -9007,7 +9007,7 @@ static int nf_tables_commit_chain_prepare(struct net *net, struct nft_chain *cha
 				continue;
 			}
 
-			if (WARN_ON_ONCE(data + expr->ops->size > data_boundary))
+			if (WARN_ON_ONCE(data + size + expr->ops->size > data_boundary))
 				return -ENOMEM;
 
 			memcpy(data + size, expr, expr->ops->size);