[PATCH 0/1] MR7960: win32u: Fix potential use of uninitialized variables.

[Yuxuan Shui (＠yshui)]

If `KeUserModeCallback` fails, `ret_ptr` and `ret_len` might be left uninitialized. Since the
returned status isn't checked in `dispatch_win_proc_params`, it can access uninitialized memory.

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One way this could actually happen is if on x86_64 `KeUserModeCallback` returned `STATUS_STACK_OVERFLOW`.