[cryptohome] make guest-mode homedir mount with -rwx------

mount.cc

 // Copyright (c) 2009-2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Contains the implementation of class Mount
 
 #include "mount.h"
 
 #include <errno.h>
 
@@ skipping 817 matching lines @@
     return true;
   }
   current_user_->Reset();
   return false;
 }
 
 bool Mount::MountGuestCryptohome() const {
   current_user_->Reset();
 
   // Attempt to mount guestfs
-  if (!platform_->Mount("guestfs", home_dir_, "tmpfs", "")) {
+  if (!platform_->Mount("guestfs", home_dir_, "tmpfs", "mode=0700")) {
     LOG(ERROR) << "Cryptohome mount failed: " << errno << " for guestfs";
     return false;
   }
   if (set_vault_ownership_) {
     if (!platform_->SetOwnership(home_dir_, default_user_, default_group_)) {
       LOG(ERROR) << "Couldn't change owner (" << default_user_ << ":"
                  << default_group_ << ") of guestfs path: "
                  << home_dir_.c_str();
       bool was_busy;
       platform_->Unmount(home_dir_.c_str(), false, &was_busy);
@@ skipping 268 matching lines @@
     if (error) {
       *error = Mount::MOUNT_ERROR_KEY_FAILURE;
     }
     return false;
   }
 
   return true;
 }
 
 } // namespace cryptohome