[PATCH nf,v2] netfilter: nf_tables: sanitize nft_set_desc_concat_parse()

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

Add several sanity checks for nft_set_desc_concat_parse():

- validate desc->field_count not larger than desc->field_len array.
- field length cannot be larger than desc->field_len (ie. U8_MAX)
- total length of the concatenation cannot be larger than register array.

Joint work with Florian Westphal.

Fixes: f3a2181e16f1 ("netfilter: nf_tables: Support for sets with multiple ranged fields")
Reported-by: <zhangziming.zzm@xxxxxxxxxxxx>
Reviewed-by: Stefano Brivio <sbrivio@xxxxxxxxxx>
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v2: - use register size per field instead of bytes to calculate concat size
    - consolidate check for too large concatenation in nft_set_desc_concat()

 net/netfilter/nf_tables_api.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index f4f1d0a2da43..dcefb5f36b3a 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4246,6 +4246,9 @@ static int nft_set_desc_concat_parse(const struct nlattr *attr,
 	u32 len;
 	int err;
 
+	if (desc->field_count >= ARRAY_SIZE(desc->field_len))
+		return -E2BIG;
+
 	err = nla_parse_nested_deprecated(tb, NFTA_SET_FIELD_MAX, attr,
 					  nft_concat_policy, NULL);
 	if (err < 0)
@@ -4255,9 +4258,8 @@ static int nft_set_desc_concat_parse(const struct nlattr *attr,
 		return -EINVAL;
 
 	len = ntohl(nla_get_be32(tb[NFTA_SET_FIELD_LEN]));
-
-	if (len * BITS_PER_BYTE / 32 > NFT_REG32_COUNT)
-		return -E2BIG;
+	if (!len || len > U8_MAX)
+		return -EINVAL;
 
 	desc->field_len[desc->field_count++] = len;
 
@@ -4268,7 +4270,8 @@ static int nft_set_desc_concat(struct nft_set_desc *desc,
 			       const struct nlattr *nla)
 {
 	struct nlattr *attr;
-	int rem, err;
+	u32 num_regs = 0;
+	int rem, err, i;
 
 	nla_for_each_nested(attr, nla, rem) {
 		if (nla_type(attr) != NFTA_LIST_ELEM)
@@ -4279,6 +4282,12 @@ static int nft_set_desc_concat(struct nft_set_desc *desc,
 			return err;
 	}
 
+	for (i = 0; i < desc->field_count; i++)
+		num_regs += DIV_ROUND_UP(desc->field_len[i], sizeof(u32));
+
+	if (num_regs > NFT_REG32_COUNT)
+		return -E2BIG;
+
 	return 0;
 }
 
-- 
2.30.2