netdev - [PATCH net 1/1] netfilter: nf_tables: reject mismatching sum of field

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Message-Id: <20250130113307.2327470-2-pablo@netfilter.org>
Date: Thu, 30 Jan 2025 12:33:07 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	fw@...len.de,
	horms@...nel.org
Subject: [PATCH net 1/1] netfilter: nf_tables: reject mismatching sum of field_len with set key length

The field length description provides the length of each separated key
field in the concatenation, each field gets rounded up to 32-bits to
calculate the pipapo rule width from pipapo_init(). The set key length
provides the total size of the key aligned to 32-bits.

Register-based arithmetics still allows for combining mismatching set
key length and field length description, eg. set key length 10 and field
description [ 5, 4 ] leading to pipapo width of 12.

Cc: stable@...r.kernel.org
Fixes: 3ce67e3793f4 ("netfilter: nf_tables: do not allow mismatch field size and set key length")
Reported-by: Noam Rathaus <noamr@...-disclosure.com>
Reviewed-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_tables_api.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index c4af283356e7..e5662dc087c8 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -5065,7 +5065,7 @@ static int nft_set_desc_concat_parse(const struct nlattr *attr,
 static int nft_set_desc_concat(struct nft_set_desc *desc,
 			       const struct nlattr *nla)
 {
-	u32 num_regs = 0, key_num_regs = 0;
+	u32 len = 0, num_regs;
 	struct nlattr *attr;
 	int rem, err, i;
 
@@ -5079,12 +5079,12 @@ static int nft_set_desc_concat(struct nft_set_desc *desc,
 	}
 
 	for (i = 0; i < desc->field_count; i++)
-		num_regs += DIV_ROUND_UP(desc->field_len[i], sizeof(u32));
+		len += round_up(desc->field_len[i], sizeof(u32));
 
-	key_num_regs = DIV_ROUND_UP(desc->klen, sizeof(u32));
-	if (key_num_regs != num_regs)
+	if (len != desc->klen)
 		return -EINVAL;
 
+	num_regs = DIV_ROUND_UP(desc->klen, sizeof(u32));
 	if (num_regs > NFT_REG32_COUNT)
 		return -E2BIG;
 
-- 
2.30.2