netfilter: nf_tables: release flow rule object from commit path

No need to postpone this to the commit release path, since no packets
are walking over this object, this is accessed from control plane only.
This helped uncovered UAF triggered by races with the netlink notifier.

Fixes: 9dd732e ("netfilter: nf_tables: memleak flow rule from commit path")
Reported-by: syzbot+8f747f62763bc6c32916@syzkaller.appspotmail.com
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: ummakynes

net/netfilter/nf_tables_api.c

@@ -8465,9 +8465,6 @@ static void nft_commit_release(struct nft_trans *trans)
 		nf_tables_chain_destroy(&trans->ctx);
 		break;
 	case NFT_MSG_DELRULE:
-		if (trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD)
-			nft_flow_rule_destroy(nft_trans_flow_rule(trans));
-
 		nf_tables_rule_destroy(&trans->ctx, nft_trans_rule(trans));
 		break;
 	case NFT_MSG_DELSET:
@@ -8973,6 +8970,9 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 			nft_rule_expr_deactivate(&trans->ctx,
 						 nft_trans_rule(trans),
 						 NFT_TRANS_COMMIT);
+
+			if (trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD)
+				nft_flow_rule_destroy(nft_trans_flow_rule(trans));
 			break;
 		case NFT_MSG_NEWSET:
 			nft_clear(net, nft_trans_set(trans));