Small extra validations on permission checks: reject "0" as a valid permission

content/browser/child_process_security_policy_impl.cc

 // Copyright (c) 2012 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 "content/browser/child_process_security_policy_impl.h"
 
 #include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 128 matching lines @@
       FilePath path;
       if (net::FileURLToFilePath(url, &path))
         return request_file_set_.find(path) != request_file_set_.end();
     }
 
     return false;  // Unmentioned schemes are disallowed.
   }
 
   // Determine if the certain permissions have been granted to a file.
   bool HasPermissionsForFile(const FilePath& file, int permissions) {
+    if (!permissions || file.empty() || !file.IsAbsolute())
+      return false;
     FilePath current_path = file.StripTrailingSeparators();
     FilePath last_path;
     int skip = 0;
     while (current_path != last_path) {
       FilePath base_name =  current_path.BaseName();
       if (base_name.value() == FilePath::kParentDirectory) {
         ++skip;
       } else if (skip > 0) {
         if (base_name.value() != FilePath::kCurrentDirectory)
           --skip;
@@ skipping 539 matching lines @@
     int permission) {
   base::AutoLock lock(lock_);
 
   SecurityStateMap::iterator state = security_state_.find(child_id);
   if (state == security_state_.end())
     return false;
   return state->second->HasPermissionsForFileSystem(filesystem_id, permission);
 }
 
 }  // namespace content