net/mpls: Implement handler for strict data checking on dumps

Without CONFIG_INET enabled compiles fail with:

net/mpls/af_mpls.o: In function `mpls_dump_routes':
af_mpls.c:(.text+0xed0): undefined reference to `ip_valid_fib_dump_req'

The preference is for MPLS to use the same handler as ipv4 and ipv6
to allow consistency when doing a dump for AF_UNSPEC which walks
all address families invoking the route dump handler. If INET is
disabled then fallback to an MPLS version which can be tighter on
the data checks.

Fixes: e8ba330ac0c5 ("rtnetlink: Update fib dumps for strict data checking")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 1 deletions

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 7f891ffffc05..5fe274c47c41 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -2031,6 +2031,40 @@ nla_put_failure:
         return -EMSGSIZE;
 }
 
+#if IS_ENABLED(CONFIG_INET)
+static int mpls_valid_fib_dump_req(const struct nlmsghdr *nlh,
+                                   struct netlink_ext_ack *extack)
+{
+        return ip_valid_fib_dump_req(nlh, extack);
+}
+#else
+static int mpls_valid_fib_dump_req(const struct nlmsghdr *nlh,
+                                   struct netlink_ext_ack *extack)
+{
+        struct rtmsg *rtm;
+
+        if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm))) {
+                NL_SET_ERR_MSG_MOD(extack, "Invalid header for FIB dump request");
+                return -EINVAL;
+        }
+
+        rtm = nlmsg_data(nlh);
+        if (rtm->rtm_dst_len || rtm->rtm_src_len  || rtm->rtm_tos   ||
+            rtm->rtm_table   || rtm->rtm_protocol || rtm->rtm_scope ||
+            rtm->rtm_type    || rtm->rtm_flags) {
+                NL_SET_ERR_MSG_MOD(extack, "Invalid values in header for FIB dump request");
+                return -EINVAL;
+        }
+
+        if (nlmsg_attrlen(nlh, sizeof(*rtm))) {
+                NL_SET_ERR_MSG_MOD(extack, "Invalid data after header in FIB dump request");
+                return -EINVAL;
+        }
+
+        return 0;
+}
+#endif
+
 static int mpls_dump_routes(struct sk_buff *skb, struct netlink_callback *cb)
 {
         const struct nlmsghdr *nlh = cb->nlh;
@@ -2042,7 +2076,7 @@ static int mpls_dump_routes(struct sk_buff *skb, struct netlink_callback *cb)
         ASSERT_RTNL();
 
         if (cb->strict_check) {
-                int err = ip_valid_fib_dump_req(nlh, cb->extack);
+                int err = mpls_valid_fib_dump_req(nlh, cb->extack);
 
                 if (err < 0)
                         return err;