8271987: Manifest improved manifest entries

Reviewed-by: rhalade, dholmes

Author: Harold Seigel

src/hotspot/share/classfile/classLoader.cpp

@@ -303,13 +303,19 @@ u1* ClassPathZipEntry::open_entry(JavaThread* current, const char* name, jint* f
   }
 
   // read contents into resource array
-  int size = (*filesize) + ((nul_terminate) ? 1 : 0);
+  size_t size = (uint32_t)(*filesize);
+  if (nul_terminate) {
+    if (sizeof(size) == sizeof(uint32_t) && size == UINT_MAX) {
+      return NULL; // 32-bit integer overflow will occur.
+    }
+    size++;
+  }
   buffer = NEW_RESOURCE_ARRAY(u1, size);
   if (!(*ReadEntry)(_zip, entry, buffer, filename)) return NULL;
 
   // return result
   if (nul_terminate) {
-    buffer[*filesize] = 0;
+    buffer[size - 1] = 0;
   }
   return buffer;
 }