netfilter: nft_exthdr: Add size check on u8 nft_exthdr attributes

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>

diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index ba7aed13e1749442d3add6fde2e6b377fd1ad39d..82c264e402781d8b8c52d04332c1b993e5c83fed 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,
                           const struct nlattr * const tb[])
 {
        struct nft_exthdr *priv = nft_expr_priv(expr);
+       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;
        priv->dreg   = nft_parse_register(tb[NFTA_EXTHDR_DREG]);
 
        return nft_validate_register_store(ctx, priv->dreg, NULL,