From 4269bba2eb79d2011a11572e9a0f681b8e9082ff Mon Sep 17 00:00:00 2001
From: Jilles Tjoelker <jilles@FreeBSD.org>
Date: Wed, 5 Sep 2018 19:16:09 +0000
Subject: [PATCH] sh: Fix formal overflow in pointer arithmetic

The intention is to lower the value of the pointer, which according to ubsan
cannot be done by adding an unsigned quantity.

Reported by:	kevans
Approved by:	re (kib)
MFC after:	1 week
---
 bin/sh/expand.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/bin/sh/expand.c b/bin/sh/expand.c
index f2287bea5605..6316400c88d5 100644
--- a/bin/sh/expand.c
+++ b/bin/sh/expand.c
@@ -896,7 +896,7 @@ reprocess(int startloc, int flag, int subtype, int quoted,
 
 	startp = stackblock() + startloc;
 	len = expdest - startp;
-	if (len >= SIZE_MAX / 2)
+	if (len >= SIZE_MAX / 2 || len > PTRDIFF_MAX)
 		abort();
 	INTOFF;
 	if (len >= buflen) {
@@ -912,7 +912,7 @@ reprocess(int startloc, int flag, int subtype, int quoted,
 	INTON;
 	memcpy(buf, startp, len);
 	buf[len] = '\0';
-	STADJUST(-len, expdest);
+	STADJUST(-(ptrdiff_t)len, expdest);
 	for (zpos = 0;;) {
 		zlen = strlen(buf + zpos);
 		strtodest(buf + zpos, flag, subtype, quoted, dst);