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Prevent out-of-bounds user image writes in menu background #2548

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Merged
ge0rdi merged 1 commit into from
Oct 5, 2026
Merged

Prevent out-of-bounds user image writes in menu background #2548

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22 changes: 16 additions & 6 deletions Src/StartMenu/StartMenuDLL/MenuPaint.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1185,13 +1185,23 @@ void CMenuContainer::CreateBackground( int width1, int width2, int height1, int

if (opacity!=MenuSkin::OPACITY_SOLID && !bMask)
{
// set to opaque
// set the visible part to opaque. BitBlt/AlphaBlend above clip to
// the destination bitmap automatically, but this direct pixel pass
// must do the same before forming a pointer into the DIB.
SelectObject(hdc,bmp0); // deselect m_Bitmap so all the GDI operations get flushed
unsigned int *bits2=bits+pos.y*totalWidth+pos.x;
alpha<<=24;
for (int y=0;y<s_Skin.User_image_size;y++,bits2+=totalWidth)
for (int x=0;x<s_Skin.User_image_size;x++)
bits2[x]=alpha|(bits2[x]&0xFFFFFF);
RECT imageRect={pos.x,pos.y,pos.x+s_Skin.User_image_size,pos.y+s_Skin.User_image_size};
RECT bitmapRect={0,0,totalWidth,totalHeight};
RECT clippedRect;
if (IntersectRect(&clippedRect,&imageRect,&bitmapRect))
{
unsigned int opaqueAlpha=alpha<<24;
for (int y=clippedRect.top;y<clippedRect.bottom;y++)
{
unsigned int *row=bits+y*totalWidth+clippedRect.left;
for (int x=clippedRect.left;x<clippedRect.right;x++,row++)
*row=opaqueAlpha|(*row&0xFFFFFF);
}
}
SelectObject(hdc,m_Bitmap);
}

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