$OpenBSD: patch-parsing_c,v 1.1 2012/10/01 16:13:23 landry Exp $
Fix for heap overflow/stack-smashing, see
http://hjemli.net/pipermail/cgit/2012-July/000652.html
http://git.zx2c4.com/cgit/commit/?id=7757d1b046ecb67b830151d20715c658867df1ec
https://bugzilla.redhat.com/show_bug.cgi?id=820733
--- parsing.c.orig	Mon Oct  1 18:05:38 2012
+++ parsing.c	Mon Oct  1 18:06:11 2012
@@ -56,6 +56,8 @@ char *substr(const char *head, const char *tail)
 {
 	char *buf;
 
+	if (tail < head)
+		return xstrdup("");
 	buf = xmalloc(tail - head + 1);
 	strncpy(buf, head, tail - head);
 	buf[tail - head] = '\0';