Avoid relying on undefined behavior in CVE-2015-1283 fix. It does not really work...

diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 7586b240220a16b349391d494b120c3495c2ea8c..620a820143c3961547b4bd7003e83fae10962dc6 100644 (file)
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -1730,7 +1730,8 @@ XML_GetBuffer(XML_Parser parser, int len)
 #ifdef XML_CONTEXT_BYTES
     int keep;
 #endif  /* defined XML_CONTEXT_BYTES */
-    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;
@@ -1761,7 +1762,8 @@ 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;