Adding guards against heap overflow in PPB_FileIO::Read

ppapi/tests/test_file_io.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 "ppapi/tests/test_file_io.h"
 
-#include <stdio.h>
 #include <string.h>
 
 #include "base/memory/scoped_ptr.h"
 #include "ppapi/c/dev/ppb_testing_dev.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/c/ppb_file_io.h"
 #include "ppapi/c/trusted/ppb_file_io_trusted.h"
 #include "ppapi/cpp/file_io.h"
 #include "ppapi/cpp/file_ref.h"
 #include "ppapi/cpp/file_system.h"
@@ skipping 232 matching lines @@
   if (rv == PP_OK_COMPLETIONPENDING)
     rv = callback.WaitForResult();
   if (rv != PP_OK)
     return ReportError("FileIO::Open", rv);
 
   // Write something to the file.
   rv = WriteEntireBuffer(instance_->pp_instance(), &file_io, 0, "test_test");
   if (rv != PP_OK)
     return ReportError("FileIO::Write", rv);
 
+  // Check for failing read operation.
+  char buf[256];
+  rv = file_io.Read(0, buf, -1,  // negative number of bytes to read
+                    callback);
+  if (rv == PP_OK_COMPLETIONPENDING)
+    rv = callback.WaitForResult();
+  if (rv != PP_ERROR_FAILED)
+    return ReportError("FileIO::Read", rv);
+
   // Read the entire file.
   std::string read_buffer;
   rv = ReadEntireFile(instance_->pp_instance(), &file_io, 0, &read_buffer);
   if (rv != PP_OK)
     return ReportError("FileIO::Read", rv);
   if (read_buffer != "test_test")
     return ReportMismatch("FileIO::Read", read_buffer, "test_test");
 
   // Truncate the file.
   rv = file_io.SetLength(4, callback);
@@ skipping 813 matching lines @@
     rv = callback.WaitForResult();
   if ((invalid_combination && rv == PP_OK) ||
       (!invalid_combination && ((rv == PP_OK) != create_if_doesnt_exist))) {
     return ReportOpenError(open_flags);
   }
 
   return std::string();
 }
 
 // TODO(viettrungluu): Test Close(). crbug.com/69457