netfilter: nfnetlink_cthelper: reject too large userspace allocation requests

Userspace should not abuse the kernel to store large amounts of data,
reject requests larger than the private area can accommodate.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nfnetlink_cthelper.c b/net/netfilter/nfnetlink_cthelper.c
index 9a50bf93dd164aad4774029ccffc21953c8b6bad..eef7120e1f741ae773a24d4ddd4ee0470f9fb4ac 100644 (file)
--- a/net/netfilter/nfnetlink_cthelper.c
+++ b/net/netfilter/nfnetlink_cthelper.c
@@ -104,7 +104,7 @@ nfnl_cthelper_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
        if (help->helper->data_len == 0)
                return -EINVAL;
 
-       memcpy(help->data, nla_data(attr), help->helper->data_len);
+       nla_memcpy(help->data, nla_data(attr), sizeof(help->data));
        return 0;
 }
 
@@ -216,6 +216,7 @@ nfnl_cthelper_create(const struct nlattr * const tb[],
 {
        struct nf_conntrack_helper *helper;
        struct nfnl_cthelper *nfcth;
+       unsigned int size;
        int ret;
 
        if (!tb[NFCTH_TUPLE] || !tb[NFCTH_POLICY] || !tb[NFCTH_PRIV_DATA_LEN])
@@ -231,7 +232,12 @@ nfnl_cthelper_create(const struct nlattr * const tb[],
                goto err1;
 
        strncpy(helper->name, nla_data(tb[NFCTH_NAME]), NF_CT_HELPER_NAME_LEN);
-       helper->data_len = ntohl(nla_get_be32(tb[NFCTH_PRIV_DATA_LEN]));
+       size = ntohl(nla_get_be32(tb[NFCTH_PRIV_DATA_LEN]));
+       if (size > FIELD_SIZEOF(struct nf_conn_help, data)) {
+               ret = -ENOMEM;
+               goto err2;
+       }
+
        helper->flags |= NF_CT_HELPER_F_USERSPACE;
        memcpy(&helper->tuple, tuple, sizeof(struct nf_conntrack_tuple));