[edk2-devel] [PATCH] MinPlatformPkg/SecFspWrapperPlatformSecLib: Change TopOfTemporaryRam type

[Chiu, Chasel]

Hi Shenglei,

Would you please elaborate a little on how casting to UINTN can resolve the overflow scenario and why 64bits OS will affect this code?

Thanks!
Chasel

> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Zhang,
> Shenglei
> Sent: Monday, September 2, 2019 8:35 PM
> To: devel at edk2.groups.io
> Cc: Kubacki, Michael A <michael.a.kubacki at intel.com>; Chiu, Chasel
> <chasel.chiu at intel.com>; Desimone, Nathaniel L
> <nathaniel.l.desimone at intel.com>; Gao, Liming <liming.gao at intel.com>
> Subject: [edk2-devel] [PATCH] MinPlatformPkg/SecFspWrapperPlatformSecLib:
> Change TopOfTemporaryRam type
> 
> Cast TopOfTemporaryRam's from UINT32 to UINTN in the expression.
> The original code (TopOfTemporaryRam - sizeof (UINT32)) may cause
> overflow. As a result the operation under 64-bit OS environment, (UINT)(...),
> may cast a overflowed 4-byte result to 8-byte one.
> 
> Cc: Michael Kubacki <michael.a.kubacki at intel.com>
> Cc: Chasel Chiu <chasel.chiu at intel.com>
> Cc: Nate DeSimone <nathaniel.l.desimone at intel.com>
> Cc: Liming Gao <liming.gao at intel.com>
> Signed-off-by: Shenglei Zhang <shenglei.zhang at intel.com>
> ---
>  .../Library/SecFspWrapperPlatformSecLib/SecGetPerformance.c     | 2 +-
>  .../SecFspWrapperPlatformSecLib/SecPlatformInformation.c        | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git
> a/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlatfor
> mSecLib/SecGetPerformance.c
> b/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlatfor
> mSecLib/SecGetPerformance.c
> index c4eeb2b1..0cc42f96 100644
> ---
> a/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlatfor
> mSecLib/SecGetPerformance.c
> +++
> b/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlat
> +++ formSecLib/SecGetPerformance.c
> @@ -79,7 +79,7 @@ SecGetPerformance (
>    //
>    TopOfTemporaryRam = (UINT32)(UINTN)TopOfTemporaryRamPpi -
> sizeof(UINT32);
>    TopOfTemporaryRam -= sizeof(UINT32) * 2;
> -  Count             = *(UINT32 *) (UINTN) (TopOfTemporaryRam - sizeof
> (UINT32));
> +  Count             = *(UINT32 *)((UINTN)TopOfTemporaryRam - sizeof
> (UINT32));
>    Size              = Count * sizeof (UINT32);
> 
>    Ticker = *(UINT64 *) (UINTN) (TopOfTemporaryRam - sizeof (UINT32) - Size
> - sizeof (UINT32) * 2); diff --git
> a/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlatfor
> mSecLib/SecPlatformInformation.c
> b/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlatfor
> mSecLib/SecPlatformInformation.c
> index 5b94ed2b..1bcee5f4 100644
> ---
> a/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlatfor
> mSecLib/SecPlatformInformation.c
> +++
> b/Platform/Intel/MinPlatformPkg/FspWrapper/Library/SecFspWrapperPlat
> +++ formSecLib/SecPlatformInformation.c
> @@ -61,7 +61,7 @@ SecPlatformInformation (
>    //
>    TopOfTemporaryRam = (UINT32)(UINTN)TopOfTemporaryRamPpi - sizeof
> (UINT32);
>    TopOfTemporaryRam -= sizeof(UINT32) * 2;
> -  Count             = *((UINT32 *)(UINTN) (TopOfTemporaryRam - sizeof
> (UINT32)));
> +  Count             = *((UINT32 *)((UINTN)TopOfTemporaryRam - sizeof
> (UINT32)));
>    Size              = Count * sizeof (IA32_HANDOFF_STATUS);
> 
>    if ((*StructureSize) < (UINT64) Size) {
> --
> 2.18.0.windows.1
> 
> 
> 


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