[PATCH 3.16 063/306] netfilter: nft_exthdr: Add size check on u8 nft_exthdr attributes

[Ben Hutchings]

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Laura Garcia Liebana <nevola@xxxxxxxxx>

commit 4da449ae1df9cfeb167e78f250b250eff64bc65e upstream.

Fix the direct assignment of offset and length attributes included in
nft_exthdr structure from u32 data to u8.

Signed-off-by: Laura Garcia Liebana <nevola@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/netfilter/nft_exthdr.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -59,6 +59,7 @@ static int nft_exthdr_init(const struct
 {
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	int err;
+	u32 offset, len;
 
 	if (tb[NFTA_EXTHDR_DREG] == NULL ||
 	    tb[NFTA_EXTHDR_TYPE] == NULL ||
@@ -66,9 +67,15 @@ static int nft_exthdr_init(const struct
 	    tb[NFTA_EXTHDR_LEN] == NULL)
 		return -EINVAL;
 
+	offset = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OFFSET]));
+	len = ntohl(nla_get_be32(tb[NFTA_EXTHDR_LEN]));
+
+	if (offset > U8_MAX || len > U8_MAX)
+		return -ERANGE;
+
 	priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
-	priv->offset = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OFFSET]));
-	priv->len    = ntohl(nla_get_be32(tb[NFTA_EXTHDR_LEN]));
+	priv->offset = offset;
+	priv->len    = len;
 	if (priv->len == 0 ||
 	    priv->len > FIELD_SIZEOF(struct nft_data, data))
 		return -EINVAL;