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Race condition with Process.GetCurrentProcess().Handle in WindowsLoader.GetAllModules #1939

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sdao opened this issue Sep 15, 2022 · 0 comments
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Race condition with Process.GetCurrentProcess().Handle in WindowsLoader.GetAllModules #1939

sdao opened this issue Sep 15, 2022 · 0 comments

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@sdao
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sdao commented Sep 15, 2022

Environment

  • Pythonnet version: 3.0.0-rc4
  • Python version: 3.7.7
  • Operating System: Windows 10 21H2
  • .NET Runtime: 5.0.17

Details

  • I think there might be a race condition in Python.Runtime.Platform.WindowsLoader.GetAllModules. I am hitting this very sporadically when I initialize Python.NET from Python. The outer and inner exceptions are:
System.TypeInitializationException: The type initializer for 'Delegates' threw an exception.
 ---> System.ComponentModel.Win32Exception (6): The handle is invalid.
   at Python.Runtime.Platform.WindowsLoader.GetAllModules() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Native/LibraryLoader.cs:line 153
   at Python.Runtime.Platform.WindowsLoader.GetFunction(IntPtr hModule, String procedureName) in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Native/LibraryLoader.cs:line 133
   at Python.Runtime.Runtime.Delegates.GetFunctionByName(String functionName, IntPtr libraryHandle) in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Runtime.Delegates.cs:line 296
   at Python.Runtime.Runtime.Delegates..cctor() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Runtime.Delegates.cs:line 110
   --- End of inner exception stack trace ---
   at Python.Runtime.Runtime.Delegates.get_PyGILState_Ensure() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Runtime.Delegates.cs:line 319
   at Python.Runtime.Runtime.PyGILState_Ensure() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Runtime.cs:line 747
   at Python.Runtime.PythonEngine.AcquireLock() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/PythonEngine.cs:line 472
   at Python.Runtime.Py.GILState..ctor() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Py.cs:line 27
   at Python.Runtime.Py.GIL() in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Py.cs:line 13
   at Python.Runtime.Loader.Initialize(IntPtr data, Int32 size) in /tmp/build-via-sdist-sstjjspf/pythonnet-3.0.0rc4/src/runtime/Loader.cs:line 26

Line numbers don't seem to line up exactly for me, but when I'm able to catch it in the debugger, it's the throw new Win32Exception() lines that trigger it.

I think what might be happening in my case is that the handle self here: https://github.com/pythonnet/pythonnet/blob/v3.0.0-rc4/src/runtime/Native/LibraryLoader.cs#L140
is being closed before one of the calls to EnumProcessModules.

The docs for Process.GetCurrentProcess() say that each invocation returns a new Process component; each instance opens its own handle to the current process, and that handle gets closed when Process.Close or Process.Dispose is called. Since a reference isn't being retained to the object returned by Process.GetCurrentProcess(), the garbage collector is able to collect it and its handle would be closed, which means that self is no longer valid.

I think one solution would be something like...

using (Process p = Process.GetCurrentProcess())
{
    EnumProcessModules(p.Handle, ...
}

in order to keep the process alive while its handle is still being accessed. Thanks!
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@filmor @sdao