From 5cfcd9ff4c1438e3865b9af03d5ff5abd5f1a7f6 Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar@redhat.com>
Date: Fri, 31 Aug 2018 09:58:52 -0700
Subject: [PATCH] MachO: Fix out-of-bounds memory access in getString16

This fixes the following tests when gcc is compiled with gcc8:

lld :: mach-o/do-not-emit-unwind-fde-arm64.yaml
lld :: mach-o/eh-frame-relocs-arm64.yaml
---
 lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h b/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h
index 407bd9b..f0340a9 100644
--- a/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h
+++ b/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h
@@ -185,12 +185,11 @@ packRelocation(const Relocation &r, bool swap, bool isBigEndian) {
   return result;
 }
 
-inline StringRef getString16(const char s[16]) {
-  StringRef x = s;
-  if ( x.size() > 16 )
-    return x.substr(0, 16);
-  else
-    return x;
+static StringRef getString16(const char s[16]) {
+  // The StringRef(const char *) constructor passes the const char * to
+  // strlen(), so we can't use this constructor here, because if there is no
+  // null terminator in s, then strlen() will read past the end of the array.
+  return StringRef(s, strnlen(s, 16));
 }
 
 inline void setString16(StringRef str, char s[16]) {
-- 
1.8.3.1