[PATCH net-next 06/12] netfilter: xt_tcpmss: add checkentry for parameter validation

[Florian Westphal <fw@strlen.de>]

From: Feng Wu <wufengwufengwufeng@gmail.com>

Add tcpmss_mt_check() that validates mss_min <= mss_max and
invert <= 1.

Signed-off-by: Feng Wu <wufengwufengwufeng@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/xt_tcpmss.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/netfilter/xt_tcpmss.c b/net/netfilter/xt_tcpmss.c
index b9da8269161d..b08b077d7f0a 100644
--- a/net/netfilter/xt_tcpmss.c
+++ b/net/netfilter/xt_tcpmss.c
@@ -78,10 +78,23 @@ tcpmss_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	return false;
 }
 
+static int tcpmss_mt_check(const struct xt_mtchk_param *par)
+{
+	const struct xt_tcpmss_match_info *info = par->matchinfo;
+
+	if (info->mss_min > info->mss_max)
+		return -EINVAL;
+	if (info->invert > 1)
+		return -EINVAL;
+
+	return 0;
+}
+
 static struct xt_match tcpmss_mt_reg[] __read_mostly = {
 	{
 		.name		= "tcpmss",
 		.family		= NFPROTO_IPV4,
+		.checkentry	= tcpmss_mt_check,
 		.match		= tcpmss_mt,
 		.matchsize	= sizeof(struct xt_tcpmss_match_info),
 		.proto		= IPPROTO_TCP,
-- 
2.54.0