[mojo-edk] Invalidate message handle when rewrite fails

mojo/edk/system/channel.cc

 // Copyright 2016 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/system/channel.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 313 matching lines @@
 bool Channel::Message::RewriteHandles(base::ProcessHandle from_process,
                                       base::ProcessHandle to_process,
                                       PlatformHandle* handles,
                                       size_t num_handles) {
   bool success = true;
   for (size_t i = 0; i < num_handles; ++i) {
     if (!handles[i].is_valid()) {
       DLOG(ERROR) << "Refusing to duplicate invalid handle.";
       continue;
     }
+    CHECK_NE(handles[i].handle, INVALID_HANDLE_VALUE);

[Ken Rockot(use gerrit already), 2016/05/03 16:46:49]

Just noticing that this can't be reached given the test above. It should be OK
for an outgoing message to contain invalid handles as long as we don't try to
dupe them.

     DCHECK_EQ(handles[i].owning_process, from_process);
     BOOL result = DuplicateHandle(
         from_process, handles[i].handle, to_process,
         &handles[i].handle, 0, FALSE,
         DUPLICATE_SAME_ACCESS | DUPLICATE_CLOSE_SOURCE);
-    if (result)
+    if (result) {
       handles[i].owning_process = to_process;
-    else
+    } else {
       success = false;
+
+      // If handle duplication fails, the source handle will already be closed
+      // due to DUPLICATE_CLOSE_SOURCE. Replace the handle in the message with
+      // an invalid handle.
+      handles[i].handle = INVALID_HANDLE_VALUE;
+      handles[i].owning_process = base::GetCurrentProcessHandle();
+    }
   }
   return success;
 }
 #endif
 
 // Helper class for managing a Channel's read buffer allocations. This maintains
 // a single contiguous buffer with the layout:
 //
 //   [discarded bytes][occupied bytes][unoccupied bytes]
 //
@@ skipping 208 matching lines @@
   return true;
 }
 
 void Channel::OnError() {
   if (delegate_)
     delegate_->OnChannelError();
 }
 
 }  // namespace edk
 }  // namespace mojo