[edk2-devel] [PATCH] UefiCpuPkg RegisterCpuFeaturesLib: NumberOfCpus may be uninitialized

[Laszlo Ersek]

On 01/21/21 10:39, Zeng, Star wrote:
> NumberOfCpus local variable in GetAcpiCpuData will be uninitialized
> when CpuS3DataDxe runs before DxeRegisterCpuFeaturesLib (linked by
> CpuFeaturesDxe) because there is no code to initialize it at
> (AcpiCpuData != NULL) execution path.
> 
> The issue is exposed after cefad282fb31aff3e1a6dcbd368cbbffc3fce900
> and 38ee7bafa72f58982f99ac6f61eef160f80bad69.

Oops, sorry!

> There was negligence in that code review.
> One further topic may be "Could EDK2 CI be enhanced to catch this kind
> of uninitialized local variable case?". :)

Indeed I don't know why none of the toolchains caught this issue in CI.
:/ GCC is otherwise known for its "variable may be used without
initialization" warnings.

> 
> This patch fixes this regression issue.
> 
> Cc: Eric Dong <eric.dong at intel.com>
> Cc: Ray Ni <ray.ni at intel.com>
> Cc: Laszlo Ersek <lersek at redhat.com>
> Signed-off-by: Star Zeng <star.zeng at intel.com>
> ---
>  .../Library/RegisterCpuFeaturesLib/RegisterCpuFeaturesLib.c      | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/RegisterCpuFeaturesLib.c b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/RegisterCpuFeaturesLib.c
> index 7bb92404027f..60daa5cc87f0 100644
> --- a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/RegisterCpuFeaturesLib.c
> +++ b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/RegisterCpuFeaturesLib.c
> @@ -957,6 +957,7 @@ GetAcpiCpuData (
>      //
>      // Allocate buffer for empty RegisterTable and PreSmmInitRegisterTable for all CPUs
>      //
> +    NumberOfCpus = AcpiCpuData->NumberOfCpus;
>      TableSize = 2 * NumberOfCpus * sizeof (CPU_REGISTER_TABLE);
>      RegisterTable  = AllocatePages (EFI_SIZE_TO_PAGES (TableSize));
>      ASSERT (RegisterTable != NULL);
> 

Reviewed-by: Laszlo Ersek <lersek at redhat.com>

(Also, I think Ray's R-b from
<https://edk2.groups.io/g/devel/message/70615> applies here, so I'm
going to pick that up.)

Thanks & sorry again
Laszlo



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