For PciIoPciRead interface, memory prior to Buffer would be written with zeros if Offset was larger than sizeof (Dev->ConfigSpace), which would cause serious system exception. So we add a pre-check branch to avoid memory override. Cc: Star Zeng <star.zeng@intel.com> Cc: Eric Dong <eric.dong@intel.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Ruiyu Ni <ruiyu.ni@intel.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Heyi Guo <heyi.guo@linaro.org> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>