From 0f4481c5e4fbc94727ae9ab2cde6a325aaf52d3d Mon Sep 17 00:00:00 2001
From: Xin LI <delphij@FreeBSD.org>
Date: Mon, 5 Mar 2007 03:07:36 +0000
Subject: [PATCH] Avoid infinite recursion on:

  echo "foo foo bar bar bar baz" | sed 's/\([^ ]*\)\( *\1\)*/\1/g'

Obtained from:	OpenBSD via NetBSD (rev. 1.18)
---
 lib/libc/regex/engine.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/libc/regex/engine.c b/lib/libc/regex/engine.c
index b8c8f49163c9..9c09efae6fa6 100644
--- a/lib/libc/regex/engine.c
+++ b/lib/libc/regex/engine.c
@@ -674,6 +674,8 @@ sopno lev;			/* PLUS nesting level */
 			return(NULL);
 		assert(m->pmatch[i].rm_so != -1);
 		len = m->pmatch[i].rm_eo - m->pmatch[i].rm_so;
+		if (len == 0)
+			return(NULL);
 		assert(stop - m->beginp >= len);
 		if (sp > stop - len)
 			return(NULL);	/* not enough left to match */