Avoid out-of-bounds read access before the beginning of the

mdoc_macros[] array.  This sometimes prevented proper warnings
about text nodes preceding the first section header.

diff --git a/usr.bin/mandoc/mdoc_validate.c b/usr.bin/mandoc/mdoc_validate.c
index a09488b..0063abd 100644 (file)
--- a/usr.bin/mandoc/mdoc_validate.c
+++ b/usr.bin/mandoc/mdoc_validate.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: mdoc_validate.c,v 1.205 2015/04/19 14:25:05 schwarze Exp $ */
+/*     $OpenBSD: mdoc_validate.c,v 1.206 2015/04/20 09:48:19 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2015 Ingo Schwarze <schwarze@openbsd.org>
@@ -1553,7 +1553,8 @@ post_root(POST_ARGS)
        /* Check that we begin with a proper `Sh'. */
 
        n = mdoc->first->child;
-       while (n != NULL && mdoc_macros[n->tok].flags & MDOC_PROLOGUE)
+       while (n != NULL && n->tok != TOKEN_NONE &&
+           mdoc_macros[n->tok].flags & MDOC_PROLOGUE)
                n = n->next;
 
        if (n == NULL)