netfilter: nft_exthdr: Add size check on u8 nft_exthdr attributes

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

diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 55c939f5371fabf35ad996efb51ea52a29630703..c04e91c5c78ea67c9f9517d6415e4216a53eb135 100644 (file)
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -59,6 +59,7 @@ static int nft_exthdr_init(const struct nft_ctx *ctx,
 {
        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 nft_ctx *ctx,
            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;