[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 <nev...@gmail.com>

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 <nev...@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 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;