Windows.h GDI - BITMAPINFO alloca indicates failure

I want to create an image from the desktop and set it to gray using BITMAPINFO, but it keeps showing me the warning, "Warning C6255 _alloca indicates failure by raising a stack overflow exception. Consider using _malloca instead". I would appreciate any advice.

HBITMAP CreateGreyscaleBitmap(int cx, int cy)
{
    BITMAPINFO* pbmi = (BITMAPINFO*)alloca(sizeof(BITMAPINFOHEADER) + sizeof(RGBQUAD) * 256);
    pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    pbmi->bmiHeader.biWidth = cx;
    pbmi->bmiHeader.biHeight = cy;
    pbmi->bmiHeader.biPlanes = 1;
    pbmi->bmiHeader.biBitCount = 8;
    pbmi->bmiHeader.biCompression = BI_RGB;
    pbmi->bmiHeader.biSizeImage = 0;
    pbmi->bmiHeader.biXPelsPerMeter = 14173;
    pbmi->bmiHeader.biYPelsPerMeter = 14173;
    pbmi->bmiHeader.biClrUsed = 0;
    pbmi->bmiHeader.biClrImportant = 0;

    for (int i = 0; i < 256; i++)
    {
        pbmi->bmiColors[i].rgbRed = i;
        pbmi->bmiColors[i].rgbGreen = i;
        pbmi->bmiColors[i].rgbBlue = i;
        pbmi->bmiColors[i].rgbReserved = 0;
    }

    PVOID pv;
    return CreateDIBSection(NULL, pbmi, DIB_RGB_COLORS, &pv, NULL, 0);
}