Fix RegisterWaitForSingleObject and SetFileCompletionNotificationModes usage

- Use .put() instead of & for wil::unique_any output parameters in
  RegisterWaitForSingleObject calls.

- Log but always complete IOCP registration when
  SetFileCompletionNotificationModes fails. Once a handle is
  associated with an IOCP via CreateIoCompletionPort, hEvent must
  be cleared and RegisteredWithIocp set regardless. Otherwise
  completions are delivered to both the event and the IOCP.

- In localhost.cpp the call remains a hard failure (THROW) since
  the accept loop requires it.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Ben Hillis

src/windows/common/relay.cpp

@@ -1149,8 +1149,8 @@ void EventHandle::Schedule()
     // If registered with an IOCP, use RegisterWaitForSingleObject to bridge the event.
     if (Iocp != nullptr && !WaitHandle)
     {
-        THROW_IF_WIN32_BOOL_FALSE(
-            RegisterWaitForSingleObject(&WaitHandle, Handle.Get(), &EventHandle::WaitCallback, this, INFINITE, WT_EXECUTEONLYONCE));
+        THROW_IF_WIN32_BOOL_FALSE(RegisterWaitForSingleObject(
+            WaitHandle.put(), Handle.Get(), &EventHandle::WaitCallback, this, INFINITE, WT_EXECUTEONLYONCE));
     }
 
     State = IOHandleStatus::Pending;
@@ -1222,9 +1222,11 @@ void ReadHandle::Register(HANDLE iocp, OverlappedIOHandle* completionTarget)
         auto result = CreateIoCompletionPort(Handle.Get(), iocp, reinterpret_cast<ULONG_PTR>(completionTarget), 0);
         if (result != nullptr)
         {
-            SetFileCompletionNotificationModes(Handle.Get(), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS);
+            LOG_IF_WIN32_BOOL_FALSE(SetFileCompletionNotificationModes(Handle.Get(), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS));
 
             // Clear the event from OVERLAPPED — completions now go to the IOCP.
+            // This must happen regardless of whether FILE_SKIP_COMPLETION_PORT_ON_SUCCESS
+            // succeeded, otherwise completions are delivered to both the event and IOCP.
             Overlapped.hEvent = nullptr;
             RegisteredWithIocp = true;
         }
@@ -1280,7 +1282,7 @@ void ReadHandle::Schedule()
         if (!RegisteredWithIocp && Iocp != nullptr && !WaitBridge)
         {
             THROW_IF_WIN32_BOOL_FALSE(RegisterWaitForSingleObject(
-                &WaitBridge, Event.get(), &ReadHandle::WaitBridgeCallback, this, INFINITE, WT_EXECUTEONLYONCE));
+                WaitBridge.put(), Event.get(), &ReadHandle::WaitBridgeCallback, this, INFINITE, WT_EXECUTEONLYONCE));
         }
     }
 }
@@ -1365,7 +1367,7 @@ void SingleAcceptHandle::Register(HANDLE iocp, OverlappedIOHandle* completionTar
         auto result = CreateIoCompletionPort(ListenSocket.Get(), iocp, reinterpret_cast<ULONG_PTR>(completionTarget), 0);
         if (result != nullptr)
         {
-            SetFileCompletionNotificationModes(ListenSocket.Get(), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS);
+            LOG_IF_WIN32_BOOL_FALSE(SetFileCompletionNotificationModes(ListenSocket.Get(), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS));
             Overlapped.hEvent = nullptr;
             RegisteredWithIocp = true;
         }
@@ -1394,7 +1396,7 @@ void SingleAcceptHandle::Schedule()
         if (!RegisteredWithIocp && Iocp != nullptr && !WaitBridge)
         {
             THROW_IF_WIN32_BOOL_FALSE(RegisterWaitForSingleObject(
-                &WaitBridge, Event.get(), &SingleAcceptHandle::WaitBridgeCallback, this, INFINITE, WT_EXECUTEONLYONCE));
+                WaitBridge.put(), Event.get(), &SingleAcceptHandle::WaitBridgeCallback, this, INFINITE, WT_EXECUTEONLYONCE));
         }
     }
 }
@@ -1621,7 +1623,7 @@ void WriteHandle::Register(HANDLE iocp, OverlappedIOHandle* completionTarget)
         auto result = CreateIoCompletionPort(Handle.Get(), iocp, reinterpret_cast<ULONG_PTR>(completionTarget), 0);
         if (result != nullptr)
         {
-            SetFileCompletionNotificationModes(Handle.Get(), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS);
+            LOG_IF_WIN32_BOOL_FALSE(SetFileCompletionNotificationModes(Handle.Get(), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS));
             Overlapped.hEvent = nullptr;
             RegisteredWithIocp = true;
         }
@@ -1660,7 +1662,7 @@ void WriteHandle::Schedule()
         if (!RegisteredWithIocp && Iocp != nullptr && !WaitBridge)
         {
             THROW_IF_WIN32_BOOL_FALSE(RegisterWaitForSingleObject(
-                &WaitBridge, Event.get(), &WriteHandle::WaitBridgeCallback, this, INFINITE, WT_EXECUTEONLYONCE));
+                WaitBridge.put(), Event.get(), &WriteHandle::WaitBridgeCallback, this, INFINITE, WT_EXECUTEONLYONCE));
         }
     }
 }

src/windows/wslrelay/localhost.cpp

@@ -676,7 +676,8 @@ void wsl::windows::wslrelay::localhost::RunWSLCPortRelay(const GUID& VmId, uint3
                     THROW_LAST_ERROR_IF_NULL(CreateIoCompletionPort(
                         reinterpret_cast<HANDLE>(e.second->ListenSocket.get()), iocp.get(), reinterpret_cast<ULONG_PTR>(e.second.get()), 0));
 
-                    SetFileCompletionNotificationModes(reinterpret_cast<HANDLE>(e.second->ListenSocket.get()), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS);
+                    THROW_IF_WIN32_BOOL_FALSE(SetFileCompletionNotificationModes(
+                        reinterpret_cast<HANDLE>(e.second->ListenSocket.get()), FILE_SKIP_COMPLETION_PORT_ON_SUCCESS));
 
                     e.second->AssociatedWithIocp = true;
                 }