netdev - [PATCH net-next 12/13] net: mpls: route: perform strict checks also for doit handlers

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Message-Id: <20190117225300.8006-13-jakub.kicinski@netronome.com>
Date:   Thu, 17 Jan 2019 14:52:59 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     davem@...emloft.net, dsahern@...il.com
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH net-next 12/13] net: mpls: route: perform strict checks also for doit handlers

Make RTM_GETROUTE's doit handler use strict checks when
NETLINK_F_STRICT_CHK is set.

Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 net/mpls/af_mpls.c | 61 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 59 insertions(+), 2 deletions(-)

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 7d55d4c04088..733c86db551b 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -2236,6 +2236,64 @@ static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt,
 		rtnl_set_sk_err(net, RTNLGRP_MPLS_ROUTE, err);
 }
 
+static int mpls_valid_getroute_req(struct sk_buff *skb,
+				   const struct nlmsghdr *nlh,
+				   struct nlattr **tb,
+				   struct netlink_ext_ack *extack)
+{
+	struct rtmsg *rtm;
+	int i, err;
+
+	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm))) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "Invalid header for get route request");
+		return -EINVAL;
+	}
+
+	if (!netlink_strict_get_check(skb))
+		return nlmsg_parse(nlh, sizeof(*rtm), tb, RTA_MAX,
+				   rtm_mpls_policy, extack);
+
+	rtm = nlmsg_data(nlh);
+	if ((rtm->rtm_dst_len && rtm->rtm_dst_len != 20) ||
+	    rtm->rtm_src_len || rtm->rtm_tos || rtm->rtm_table ||
+	    rtm->rtm_protocol || rtm->rtm_scope || rtm->rtm_type) {
+		NL_SET_ERR_MSG_MOD(extack, "Invalid values in header for get route request");
+		return -EINVAL;
+	}
+	if (rtm->rtm_flags & ~RTM_F_FIB_MATCH) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "Invalid flags for get route request");
+		return -EINVAL;
+	}
+
+	err = nlmsg_parse_strict(nlh, sizeof(*rtm), tb, RTA_MAX,
+				 rtm_mpls_policy, extack);
+	if (err)
+		return err;
+
+	if ((tb[RTA_DST] || tb[RTA_NEWDST]) && !rtm->rtm_dst_len) {
+		NL_SET_ERR_MSG_MOD(extack, "rtm_dst_len must be 20 for MPLS");
+		return -EINVAL;
+	}
+
+	for (i = 0; i <= RTA_MAX; i++) {
+		if (!tb[i])
+			continue;
+
+		switch (i) {
+		case RTA_DST:
+		case RTA_NEWDST:
+			break;
+		default:
+			NL_SET_ERR_MSG_MOD(extack, "Unsupported attribute in get route request");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 static int mpls_getroute(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
 			 struct netlink_ext_ack *extack)
 {
@@ -2255,8 +2313,7 @@ static int mpls_getroute(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
 	u8 n_labels;
 	int err;
 
-	err = nlmsg_parse(in_nlh, sizeof(*rtm), tb, RTA_MAX,
-			  rtm_mpls_policy, extack);
+	err = mpls_valid_getroute_req(in_skb, in_nlh, tb, extack);
 	if (err < 0)
 		goto errout;
 
-- 
2.19.2