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

[Jakub Kicinski]

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

Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.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