Re: [PATCH] MdePkg UefiLib: Check Table against NULL in ScanTableInSDT

["Gao, Liming" <liming.gao@intel.com>]

Reviewed-by: Liming Gao <liming.gao@intel.com>

> -----Original Message-----
> From: Zeng, Star
> Sent: Friday, October 19, 2018 4:07 PM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Gao, Liming <liming.gao@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>; Wang,
> Jian J <jian.j.wang@intel.com>
> Subject: [PATCH] MdePkg UefiLib: Check Table against NULL in ScanTableInSDT
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1266
> 
> af5e95215928e052445c473f1244412dadea8252 abstracted generic functions
> from different modules (IntelVTdDxe, S3SaveStateDxe, PcRtc,
> DpDynamicCommand and PiSmmCpuDxeSmm). Some of them (IntelVTdDxe and
> PcRtc) checked Table against NULL before accessing Table->Signature,
> some (S3SaveStateDxe, DpDynamicCommand and PiSmmCpuDxeSmm did not.
> 
> The ScanTableInSDT() in Acpi.c of UefiLib was mainly from
> S3SaveStateDxe, so it does not check Table against NULL before
> accessing Table->Signature.
> 
> This patch updates ScanTableInSDT() to check Table against NULL first
> before accessing Table->Signature.
> 
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Star Zeng <star.zeng@intel.com>
> ---
>  MdePkg/Library/UefiLib/Acpi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/MdePkg/Library/UefiLib/Acpi.c b/MdePkg/Library/UefiLib/Acpi.c
> index 4df6731ff0a4..59a828835ca0 100644
> --- a/MdePkg/Library/UefiLib/Acpi.c
> +++ b/MdePkg/Library/UefiLib/Acpi.c
> @@ -67,7 +67,7 @@ ScanTableInSDT (
>      EntryPtr = 0;
>      CopyMem (&EntryPtr, (VOID *)(BasePtr + Index * TablePointerSize), TablePointerSize);
>      Table = (EFI_ACPI_COMMON_HEADER *)((UINTN)(EntryPtr));
> -    if (Table->Signature == Signature) {
> +    if ((Table != NULL) && (Table->Signature == Signature)) {
>        if (PreviousTable != NULL) {
>          if (Table == PreviousTable) {
>            *PreviousTableLocated = TRUE;
> --
> 2.7.0.windows.1