[PATCH nf 1/1] netfilter: expect: Make sure the max_expected limit is effective

[gfree.wind@foxmail.com]

From: Gao Feng <fgao@ikuai8.com>

Because the type of expecting, the member of nf_conn_help, is u8, it
would overflow after reach U8_MAX(255). So it doesn't work when we
configure the max_expected exceeds 255 with expect policy.

Now add the check for max_expected. Return the -EINVAL when it exceeds
the limit.

Signed-off-by: Gao Feng <fgao@ikuai8.com>
---
 include/net/netfilter/nf_conntrack_expect.h | 1 +
 net/netfilter/nf_conntrack_helper.c         | 3 +++
 net/netfilter/nfnetlink_cthelper.c          | 4 ++++
 3 files changed, 8 insertions(+)

diff --git a/include/net/netfilter/nf_conntrack_expect.h b/include/net/netfilter/nf_conntrack_expect.h
index 5ed33ea..aa36a31 100644
--- a/include/net/netfilter/nf_conntrack_expect.h
+++ b/include/net/netfilter/nf_conntrack_expect.h
@@ -71,6 +71,7 @@ struct nf_conntrack_expect_policy {
 };
 
 #define NF_CT_EXPECT_CLASS_DEFAULT	0
+#define NF_CT_EXPECT_MAX_CNT		U8_MAX
 
 int nf_conntrack_expect_pernet_init(struct net *net);
 void nf_conntrack_expect_pernet_fini(struct net *net);
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 6dc44d9..752a977 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -385,6 +385,9 @@ int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 	BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 
+	if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
+		return -EINVAL;
+
 	mutex_lock(&nf_ct_helper_mutex);
 	hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
 		if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple, &mask)) {
diff --git a/net/netfilter/nfnetlink_cthelper.c b/net/netfilter/nfnetlink_cthelper.c
index 2b987d2..de841b3 100644
--- a/net/netfilter/nfnetlink_cthelper.c
+++ b/net/netfilter/nfnetlink_cthelper.c
@@ -143,6 +143,8 @@
 		nla_data(tb[NFCTH_POLICY_NAME]), NF_CT_HELPER_NAME_LEN);
 	expect_policy->max_expected =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_MAX]));
+	if (expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
+		return -EINVAL;
 	expect_policy->timeout =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_TIMEOUT]));
 
@@ -280,6 +282,8 @@
 
 	new_policy->max_expected =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_MAX]));
+	if (new_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
+		return -EINVAL;
 	new_policy->timeout =
 		ntohl(nla_get_be32(tb[NFCTH_POLICY_EXPECT_TIMEOUT]));
 
-- 
1.9.1