netfilter: nf_tables: fix nft_trans type confusion

[ Upstream commit e3c361b8acd636f5fe80c02849ca175201edf10c ]

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@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 091df8a7cb1e75b8fb6b3d07affe62bb8620b12b..f20244a91d781ee077a41b693a62fd94e7e07dbc 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3595,12 +3595,10 @@ 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);
 }