[PATCH net-next 07/12] netfilter: xt_dscp: add checkentry for tos match

[Florian Westphal <fw@strlen.de>]

From: Feng Wu <wufengwufengwufeng@gmail.com>

The 'tos' match registered in xt_dscp.c has no .checkentry callback,
allowing userspace to insert rules with a non-boolean invert field
without any validation.

Add tos_mt_check() that rejects invert > 1 and attach it to both the
IPv4 and IPv6 'tos' match registrations.

Signed-off-by: Feng Wu <wufengwufengwufeng@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/xt_dscp.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/netfilter/xt_dscp.c b/net/netfilter/xt_dscp.c
index fb0169a8f9bb..878f27016e99 100644
--- a/net/netfilter/xt_dscp.c
+++ b/net/netfilter/xt_dscp.c
@@ -49,6 +49,16 @@ static int dscp_mt_check(const struct xt_mtchk_param *par)
 	return 0;
 }
 
+static int tos_mt_check(const struct xt_mtchk_param *par)
+{
+	const struct xt_tos_match_info *info = par->matchinfo;
+
+	if (info->invert > 1)
+		return -EINVAL;
+
+	return 0;
+}
+
 static bool tos_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_tos_match_info *info = par->matchinfo;
@@ -82,6 +92,7 @@ static struct xt_match dscp_mt_reg[] __read_mostly = {
 		.name		= "tos",
 		.revision	= 1,
 		.family		= NFPROTO_IPV4,
+		.checkentry	= tos_mt_check,
 		.match		= tos_mt,
 		.matchsize	= sizeof(struct xt_tos_match_info),
 		.me		= THIS_MODULE,
@@ -90,6 +101,7 @@ static struct xt_match dscp_mt_reg[] __read_mostly = {
 		.name		= "tos",
 		.revision	= 1,
 		.family		= NFPROTO_IPV6,
+		.checkentry	= tos_mt_check,
 		.match		= tos_mt,
 		.matchsize	= sizeof(struct xt_tos_match_info),
 		.me		= THIS_MODULE,
-- 
2.54.0