netdev - [PATCH v2 net-next 2/5] l2tp: double-check l2specific

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Message-Id: <119b4940ea365493fbf3c22f5f485ee800254fb3.1515940731.git.lorenzo.bianconi@redhat.com>
Date:   Sun, 14 Jan 2018 15:50:55 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, jchapman@...alix.com, g.nault@...halink.fr
Subject: [PATCH v2 net-next 2/5] l2tp: double-check l2specific_type provided by userspace

Add sanity check on l2specific_type provided by userspace in
l2tp_nl_cmd_session_create() since just L2TP_L2SPECTYPE_DEFAULT and
L2TP_L2SPECTYPE_NONE are currently supported.
Moreover do not always initialize l2specific_type if userspace requests
a given l2-specific sublayer type

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
---
 net/l2tp/l2tp_netlink.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 48b5bf30ec50..711cf208f23a 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -550,9 +550,16 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
 		if (info->attrs[L2TP_ATTR_DATA_SEQ])
 			cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
 
-		cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
-		if (info->attrs[L2TP_ATTR_L2SPEC_TYPE])
+		if (info->attrs[L2TP_ATTR_L2SPEC_TYPE]) {
 			cfg.l2specific_type = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_TYPE]);
+			if (cfg.l2specific_type != L2TP_L2SPECTYPE_DEFAULT &&
+			    cfg.l2specific_type != L2TP_L2SPECTYPE_NONE) {
+				ret = -EINVAL;
+				goto out_tunnel;
+			}
+		} else {
+			cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
+		}
 
 		cfg.l2specific_len = 4;
 		if (info->attrs[L2TP_ATTR_L2SPEC_LEN])
-- 
2.13.6