netdev - [PATCH net 2/3] netfilter: nf_tables: fix nft

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Message-Id: <20230517123756.7353-3-fw@strlen.de>
Date: Wed, 17 May 2023 14:37:55 +0200
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Paolo Abeni <pabeni@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	<netfilter-devel@...r.kernel.org>
Subject: [PATCH net 2/3] netfilter: nf_tables: fix nft_trans type confusion

nft_trans_FOO objects all share a common nft_trans base structure, but
trailing fields depend on the real object size. Access is only safe after
trans->msg_type check.

Check for rule type first.  Found by code inspection.

Fixes: 1a94e38d254b ("netfilter: nf_tables: add NFTA_RULE_ID attribute")
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/netfilter/nf_tables_api.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 59fb8320ab4d..dc5675962de4 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3865,12 +3865,10 @@ static struct nft_rule *nft_rule_lookup_byid(const struct net *net,
 	struct nft_trans *trans;
 
 	list_for_each_entry(trans, &nft_net->commit_list, list) {
-		struct nft_rule *rule = nft_trans_rule(trans);
-
 		if (trans->msg_type == NFT_MSG_NEWRULE &&
 		    trans->ctx.chain == chain &&
 		    id == nft_trans_rule_id(trans))
-			return rule;
+			return nft_trans_rule(trans);
 	}
 	return ERR_PTR(-ENOENT);
 }
-- 
2.39.3