WPA CLI Bug

To reproduce the bug just download this project, build and run it locally and watch the output.

Project link: https://github.com/nader-zouaoui/WPA-CLI-bug/tree/master

The project is a clean C# WPF project that has only one button when you click it it's supposed to call wpa -listplugins and print the output to the Debug output.

The wpa call was made using the Process class from C#, below is a snippet of how it was made:

        public static void StartMe()
        {
            Debug.WriteLine("I was called");
            try
            {
                using (Process myProcess = new Process())
                {
                    myProcess.StartInfo.UseShellExecute = false;
                    myProcess.StartInfo.FileName = "C:\\Program Files (x86)\\Windows Kits\\10\\Windows Performance Toolkit\\wpa.exe";
                    myProcess.StartInfo.CreateNoWindow = true;
                    myProcess.StartInfo.RedirectStandardOutput = true;
                    myProcess.StartInfo.RedirectStandardError = true;
                    myProcess.OutputDataReceived += MainWindow.p_OutputDataReceived;
                    myProcess.ErrorDataReceived += MainWindow.p_ErrorDataReceived;
                    myProcess.StartInfo.ArgumentList.Add("-listplugins");
                    myProcess.Start();
                    myProcess.BeginOutputReadLine();
                    myProcess.BeginErrorReadLine();
                    myProcess.WaitForExit();
                }
            }
            catch (Exception e)
            {
                Debug.WriteLine(e.Message);
            }
        }

Expected behaviour

We are using the Process class to call the wpa cli with -listplugins argument to get the list of the plugin. This whole process is triggered after clicking on a button using the Click Button attribute. We expect the button to print the list of the available plugins to the Debug console.

Observed behaviour

After clicking the button the UI is blocked and the WPACall_Click function keeps getting called over and over in a infinite loop (Example Image on the github Readme.md)

Why this is happening (Speculative analysis)

I believe that the wpa CLI is sending a ENTER keystroke after exiting and since the button is on focuse it gets clicked again and the cycle keeps repeating.

Other observed patterns

• After calling wpa -listplugins on the command line directly I saw that the shell is being released for a brief moment (where you can type other commands if you wish) and then when the result of wpa -listplugins is ready, it gets appended in the shell output. (Example Image on the github Readme.md)
• When we try to call that using the following pattern cmd /c "wpa -listplugins" we also realize that the result is printed and then an extra ENTER stroke is called (Example Image on the github Readme.md)

A fix that reinforces the theory

If swap the Click attribute from the button to a LeftMouseDown attribute the bug disappears.

Also when logging the call stack frames we immidiatly see a small difference betweeen the original call (the one triggerd by my mouse click) and the looped calls (The one presumably triggered by the ENTER keystroke), We can see that the second call onwards are all being triggered by an OnKeyDown event rather than OnLeftMouseUp event.

Stacktraces

Stack trace for original run

   at WPABug.MainWindow.WPACall_Click(Object sender, RoutedEventArgs e)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at WPABug.App.Main()

Stack trace for looped runs

   at WPABug.MainWindow.WPACall_Click(Object sender, RoutedEventArgs e)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at WPABug.App.Main()