[PATCH 0/1] MR4434: winex11: Free correct pointer when using xf86vm

[Fabian Maurer (＠DarkShadow44)]

After allocation the pointer gets shifted by sizeof(xf86vm_modes),
so we have to undo that before calling free.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55909

[PATCH 1/1] winex11: Free correct pointer when using xf86vm

[Fabian Maurer]

From: Fabian Maurer

After allocation the pointer gets shifted by sizeof(xf86vm_modes),
so we have to undo that before calling free.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55909
---
 dlls/winex11.drv/xvidmode.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/dlls/winex11.drv/xvidmode.c b/dlls/winex11.drv/xvidmode.c
index 399d5e90e1e..4563b728a41 100644
--- a/dlls/winex11.drv/xvidmode.c
+++ b/dlls/winex11.drv/xvidmode.c
@@ -156,14 +156,15 @@ static BOOL xf86vm_get_modes(x11drv_settings_id id, DWORD flags, DEVMODEW **new_
 static void xf86vm_free_modes(DEVMODEW *modes)
 {
     XF86VidModeModeInfo **xf86vm_modes;
+    BYTE *ptr = (BYTE *)modes - sizeof(xf86vm_modes);

if (modes)
     {
         assert(modes[0].dmDriverExtra == sizeof(XF86VidModeModeInfo *));
-        memcpy(&xf86vm_modes, (BYTE *)modes - sizeof(xf86vm_modes), sizeof(xf86vm_modes));
+        memcpy(&xf86vm_modes, ptr, sizeof(xf86vm_modes));
         XFree(xf86vm_modes);
     }
-    free(modes);
+    free(ptr);
 }

static BOOL xf86vm_get_current_mode(x11drv_settings_id id, DEVMODEW *mode)

[Zhiyi Zhang (＠zhiyi)]

Zhiyi Zhang (@zhiyi) commented about dlls/winex11.drv/xvidmode.c:
> static void xf86vm_free_modes(DEVMODEW *modes)
>  {
>      XF86VidModeModeInfo **xf86vm_modes;
> -
>
> BYTE *ptr = (BYTE *)modes - sizeof(xf86vm_modes);
>
> if (modes)
> {
>     assert(modes[0].dmDriverExtra == sizeof(XF86VidModeModeInfo *));
> -
>    memcpy(&xf86vm_modes, (BYTE *)modes - sizeof(xf86vm_modes), sizeof(xf86vm_modes));
> -
>    memcpy(&xf86vm_modes, ptr, sizeof(xf86vm_modes));
>    XFree(xf86vm_modes);

Let's move free(ptr) into the if (modes) branch or return early if modes is NULL.