https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2015-2716

Address CVE-2015-2716, which was also called CVE-2015-1283.

https://github.com/libexpat/libexpat/commit/ba0f9c3b40c264b8dd392e02a7a060a8fa54f032.patch
https://github.com/libexpat/libexpat/commit/f0bec73b018caa07d3e75ec8dd967f3785d71bde.patch

--- expat-2.1.0/lib/xmlparse.c.cve2716
+++ expat-2.1.0/lib/xmlparse.c
@@ -1678,6 +1678,10 @@
 void * XMLCALL
 XML_GetBuffer(XML_Parser parser, int len)
 {
+  if (len < 0) {
+    errorCode = XML_ERROR_NO_MEMORY;
+    return NULL;
+  }
   switch (ps_parsing) {
   case XML_SUSPENDED:
     errorCode = XML_ERROR_SUSPENDED;
@@ -1689,8 +1693,11 @@
   }
 
   if (len > bufferLim - bufferEnd) {
-    /* FIXME avoid integer overflow */
-    int neededSize = len + (int)(bufferEnd - bufferPtr);
+    int neededSize = (int) ((unsigned)len + (unsigned)(bufferEnd - bufferPtr));
+    if (neededSize < 0) {
+      errorCode = XML_ERROR_NO_MEMORY;
+      return NULL;
+    }
 #ifdef XML_CONTEXT_BYTES
     int keep = (int)(bufferPtr - buffer);
 
@@ -1718,8 +1725,13 @@
       if (bufferSize == 0)
         bufferSize = INIT_BUFFER_SIZE;
       do {
-        bufferSize *= 2;
-      } while (bufferSize < neededSize);
+        /* Do not invoke signed arithmetic overflow: */
+        bufferSize = (int) (2U * (unsigned) bufferSize);
+      } while (bufferSize < neededSize && bufferSize > 0);
+      if (bufferSize <= 0) {
+        errorCode = XML_ERROR_NO_MEMORY;
+        return NULL;
+      }
       newBuf = (char *)MALLOC(bufferSize);
       if (newBuf == 0) {
         errorCode = XML_ERROR_NO_MEMORY;