Re: [edk2-devel] [PATCH 1/1] IntelFsp2Pkg/Library/BaseFspCommonLib: Fix OVERRUN Coverity issue

["Pedro Falcato" <pedro.falcato@gmail.com>]

On Thu, May 18, 2023 at 4:16 PM Ranbir Singh <rsingh@ventanamicro.com> wrote:
>
> FspData->PerfIdx is getting increased for every call unconditionally
> in the function SetFspMeasurePoint and hence memory access can happen
> for out of bound FspData->PerfData[] array entries also.
>
> Example -
>    FspData->PerfData is an array of 32 UINT64 entries. Assume a call
>    is made to SetFspMeasurePoint function when the FspData->PerfIdx
>    last value is 31. It gets incremented to 32 at line 400.
>    Any subsequent call to SetFspMeasurePoint functions leads to
>    FspData->PerfData[32] getting accessed which is out of the PerfData
>    array as well as the FSP_GLOBAL_DATA structure boundary.
>
> Hence keep array access and index increment inside if block only and
> return invalid performance timestamp when PerfIdx is invalid.
>
> Cc: Chasel Chiu <chasel.chiu@intel.com>
> Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4200
> Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com>
> Signed-off-by: Ranbir Singh <rsingh@ventanamicro.com>
> ---
>  IntelFsp2Pkg/Library/BaseFspCommonLib/FspCommonLib.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/IntelFsp2Pkg/Library/BaseFspCommonLib/FspCommonLib.c b/IntelFsp2Pkg/Library/BaseFspCommonLib/FspCommonLib.c
> index a22b0e7825ad..cda2a7b2478e 100644
> --- a/IntelFsp2Pkg/Library/BaseFspCommonLib/FspCommonLib.c
> +++ b/IntelFsp2Pkg/Library/BaseFspCommonLib/FspCommonLib.c
> @@ -377,7 +377,8 @@ GetFspSiliconInitUpdDataPointer (
>
>    @param[in] Id       Measurement point ID.
>
> -  @return performance timestamp.
> +  @return performance timestamp if current PerfIdx is valid,
> +          else return 0 as invalid performance timestamp
>  **/
>  UINT64
>  EFIAPI
> @@ -395,9 +396,10 @@ SetFspMeasurePoint (
>    if (FspData->PerfIdx < sizeof (FspData->PerfData) / sizeof (FspData->PerfData[0])) {
>      FspData->PerfData[FspData->PerfIdx]                  = AsmReadTsc ();
>      ((UINT8 *)(&FspData->PerfData[FspData->PerfIdx]))[7] = Id;
> +    return FspData->PerfData[(FspData->PerfIdx)++];
>    }
>
> -  return FspData->PerfData[(FspData->PerfIdx)++];
> +  return (UINT64)0x0000000000000000;

return 0;

Works just as well. You also don't need a cast.

https://godbolt.org/z/e5vvGcWWo

-- 
Pedro