make sure we've read the lenght bytes before checking the length

ok benno@

diff --git a/sbin/slaacd/frontend.c b/sbin/slaacd/frontend.c
index c2c6637..4e3cd16 100644 (file)
--- a/sbin/slaacd/frontend.c
+++ b/sbin/slaacd/frontend.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: frontend.c,v 1.12 2018/02/19 09:52:16 otto Exp $      */
+/*     $OpenBSD: frontend.c,v 1.13 2018/02/20 16:22:19 otto Exp $      */
 
 /*
  * Copyright (c) 2017 Florian Obser <florian@openbsd.org>
@@ -652,7 +652,7 @@ route_receive(int fd, short events, void *arg)
        if (n == 0)
                fatal("routing socket closed");
 
-       if (n < rtm->rtm_msglen) {
+       if (n < (ssize_t)sizeof(rtm->rtm_msglen) || n < rtm->rtm_msglen) {
                log_warnx("partial rtm of %zd in buffer", n);
                return;
        }