Reduce memory and time consumption on certain malformed input files

by limiting the length of expanded input lines during the
(usually recursive) expansion of user defined strings.
Resource hogging found by jsg@ with afl.

1 files changed, 8 insertions, 1 deletions

diff --git a/roff.c b/roff.c
index 992d9772..8f67e84d 100644
--- a/roff.c
+++ b/roff.c
@@ -1,4 +1,4 @@
-/*	$Id: roff.c,v 1.244 2014/12/18 17:43:41 schwarze Exp $ */
+/*	$Id: roff.c,v 1.245 2014/12/25 17:23:32 schwarze Exp $ */
 /*
  * Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2014 Ingo Schwarze <schwarze@openbsd.org>
@@ -21,6 +21,7 @@
 
 #include <assert.h>
 #include <ctype.h>
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -658,6 +659,12 @@ roff_res(struct roff *r, struct buf *buf, int ln, int pos)
 		buf->sz = mandoc_asprintf(&nbuf, "%s%s%s",
 		    buf->buf, res, cp) + 1;
 
+		if (buf->sz > SHRT_MAX) {
+			mandoc_msg(MANDOCERR_ROFFLOOP, r->parse,
+			    ln, (int)(stesc - buf->buf), NULL);
+			return(ROFF_IGN);
+		}
+
 		/* Prepare for the next replacement. */
 
 		start = nbuf + pos;