Mojo EDK: Fix race in named pipe creation for tests

mojo/edk/test/multiprocess_test_helper.cc

 // Copyright 2013 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 "mojo/edk/test/multiprocess_test_helper.h"
 
 #include <functional>
 #include <set>
 #include <utility>
 
@@ skipping 122 matching lines @@
 #elif defined(OS_WIN)
   options.start_hidden = true;
   if (base::win::GetVersion() >= base::win::VERSION_VISTA)
     options.handles_to_inherit = &handle_passing_info;
   else
     options.inherit_handles = true;
 #else
 #error "Not supported yet."
 #endif
 
+  // NOTE: In the case of named pipes, it's important that the server handle be
+  // created before the child process is launched; otherwise the server binding
+  // the pipe path can race with child's connection to the pipe.
+  ScopedPlatformHandle server_handle;
+  if (launch_type == LaunchType::CHILD || launch_type == LaunchType::PEER) {
+    server_handle = channel.PassServerHandle();
+  } else if (launch_type == LaunchType::NAMED_CHILD ||
+             launch_type == LaunchType::NAMED_PEER) {
+    server_handle = CreateServerHandle(named_pipe);
+  }
+
   ScopedMessagePipeHandle pipe;
   std::string child_token = mojo::edk::GenerateRandomToken();
   if (launch_type == LaunchType::CHILD ||
       launch_type == LaunchType::NAMED_CHILD) {
     pipe = CreateParentMessagePipe(pipe_token, child_token);
-  } else if (launch_type == LaunchType::PEER) {
+  } else if (launch_type == LaunchType::PEER ||
+             launch_type == LaunchType::NAMED_PEER) {
     peer_token_ = mojo::edk::GenerateRandomToken();
-    pipe = ConnectToPeerProcess(channel.PassServerHandle(), peer_token_);
-  } else if (launch_type == LaunchType::NAMED_PEER) {
-    peer_token_ = mojo::edk::GenerateRandomToken();
-    pipe = ConnectToPeerProcess(CreateServerHandle(named_pipe), peer_token_);
+    pipe = ConnectToPeerProcess(std::move(server_handle), peer_token_);
   }
 
   test_child_ =
       base::SpawnMultiProcessTestChild(test_child_main, command_line, options);
   if (launch_type == LaunchType::CHILD || launch_type == LaunchType::PEER)
     channel.ChildProcessLaunched();
 
-  if (launch_type == LaunchType::CHILD) {
-    ChildProcessLaunched(test_child_.Handle(), channel.PassServerHandle(),
-                         child_token, process_error_callback_);
-  } else if (launch_type == LaunchType::NAMED_CHILD) {
-    ChildProcessLaunched(test_child_.Handle(), CreateServerHandle(named_pipe),
+  if (launch_type == LaunchType::CHILD ||
+      launch_type == LaunchType::NAMED_CHILD) {
+    DCHECK(server_handle.is_valid());
+    ChildProcessLaunched(test_child_.Handle(), std::move(server_handle),
                          child_token, process_error_callback_);
   }
 
   CHECK(test_child_.IsValid());
   return pipe;
 }
 
 int MultiprocessTestHelper::WaitForChildShutdown() {
   CHECK(test_child_.IsValid());
 
@@ skipping 70 matching lines @@
             ::testing::Test::HasNonfatalFailure()) ? 1 : 0;
   });
 }
 
 // static
 mojo::ScopedMessagePipeHandle MultiprocessTestHelper::primordial_pipe;
 
 }  // namespace test
 }  // namespace edk
 }  // namespace mojo