[PATCH 0/1] MR3755: win32u: Correct the packed size of WM_GETDLGCODE when lparam is NULL.

[Tim Clem (＠tclem)]

If lparam is null, the current code crashes when it hits the memcpy in pack_user_message.

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https://gitlab.winehq.org/wine/wine/-/merge_requests/3755

[PATCH 1/1] win32u: Correct the packed size of WM_GETDLGCODE when lparam is NULL.

[Tim Clem]

From: Tim Clem <tclem(a)codeweavers.com>

---
 dlls/win32u/message.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dlls/win32u/message.c b/dlls/win32u/message.c
index d15f9af3f9f..d2909339983 100644
--- a/dlls/win32u/message.c
+++ b/dlls/win32u/message.c
@@ -1691,7 +1691,7 @@ size_t user_message_size( HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam,
         size = sizeof(STYLESTRUCT);
         break;
     case WM_GETDLGCODE:
-        size = sizeof(MSG);
+        if (lparam) size = sizeof(MSG);
         break;
     case SBM_SETSCROLLINFO:
     case SBM_GETSCROLLINFO:
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/3755

[Jacek Caban (＠jacek)]

The fix looks good, but it would be nice to have a test. Please include something like the [attached test](/uploads/4ff2f549a3d6edd1d7076f2968c584e2/patch.diff).

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/3755#note_44688