From 29a11774d8ebbafe8418b4a5ffb4cc1160b194a1 Mon Sep 17 00:00:00 2001
From: Pascal Cuoq <cuoq@trust-in-soft.com>
Date: Sun, 15 May 2016 09:05:46 +0200
Subject: [PATCH] Avoid relying on undefined behavior in CVE-2015-1283 fix. It
 does not really work: https://godbolt.org/g/Zl8gdF

---
 expat/lib/xmlparse.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 13e080d..cdb12ef 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -1693,7 +1693,8 @@ XML_GetBuffer(XML_Parser parser, int len)
   }
 
   if (len > bufferLim - bufferEnd) {
-    int neededSize = len + (int)(bufferEnd - bufferPtr);
+    /* Do not invoke signed arithmetic overflow: */
+    int neededSize = (int) ((unsigned)len + (unsigned)(bufferEnd - bufferPtr));
     if (neededSize < 0) {
       errorCode = XML_ERROR_NO_MEMORY;
       return NULL;
@@ -1725,7 +1726,8 @@ XML_GetBuffer(XML_Parser parser, int len)
       if (bufferSize == 0)
         bufferSize = INIT_BUFFER_SIZE;
       do {
-        bufferSize *= 2;
+        /* Do not invoke signed arithmetic overflow: */
+        bufferSize = (int) (2U * (unsigned) bufferSize);
       } while (bufferSize < neededSize && bufferSize > 0);
       if (bufferSize <= 0) {
         errorCode = XML_ERROR_NO_MEMORY;
-- 
2.8.2