Adding guards against heap overflow in PPB_FileIO::Read

base/file_util_proxy.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/file_util_proxy.h"
 
 #include "base/message_loop_proxy.h"
 
 // TODO(jianli): Move the code from anonymous namespace to base namespace so
 // that all of the base:: prefixes would be unnecessary.
@@ skipping 836 matching lines @@
                new RelayDelete(file_path, true, callback));
 }
 
 // static
 bool FileUtilProxy::Read(
     scoped_refptr<MessageLoopProxy> message_loop_proxy,
     PlatformFile file,
     int64 offset,
     int bytes_to_read,
     ReadCallback* callback) {
+  if (bytes_to_read < 0)
+    return false;
   return Start(FROM_HERE, message_loop_proxy,
                new RelayRead(file, offset, bytes_to_read, callback));
 }
 
 // static
 bool FileUtilProxy::Write(
     scoped_refptr<MessageLoopProxy> message_loop_proxy,
     PlatformFile file,
     int64 offset,
     const char* buffer,
@@ skipping 49 matching lines @@
 
 // static
 bool FileUtilProxy::Flush(
     scoped_refptr<MessageLoopProxy> message_loop_proxy,
     PlatformFile file,
     StatusCallback* callback) {
   return Start(FROM_HERE, message_loop_proxy, new RelayFlush(file, callback));
 }
 
 }  // namespace base