Re: [edk2-devel] [PATCH v2 1/3] UefiCpuPkg/CpuPageTableLib: Init local variable before using it.

["Ni, Ray" <ray.ni@intel.com>]

Reviewed-by: Ray Ni <ray.ni@intel.com>

Thanks,
Ray
> -----Original Message-----
> From: Liu, Zhiguang <zhiguang.liu@intel.com>
> Sent: Thursday, November 30, 2023 2:29 PM
> To: devel@edk2.groups.io
> Cc: Liu, Zhiguang <zhiguang.liu@intel.com>; Ni, Ray <ray.ni@intel.com>;
> Kumar, Rahul R <rahul.r.kumar@intel.com>; Gerd Hoffmann
> <kraxel@redhat.com>; Laszlo Ersek <lersek@redhat.com>
> Subject: [PATCH v2 1/3] UefiCpuPkg/CpuPageTableLib: Init local variable
> before using it.
> 
> The local variable OneOfPagingEntry is used before initialized, this
> may cause reserved bit in page table entry is set especially in PAE
> paging mode. The bug is random because it depends on the value in
> stack.
> 
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
> ---
>  UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> index eff02619fa..36b2c4e6a3 100644
> --- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> +++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> @@ -338,7 +338,7 @@ PageTableLibMapInLevel (
>    ParentAttribute             = &LocalParentAttribute;
> 
>    OriginalParentPagingEntry.Uint64 = ParentPagingEntry->Uint64;
> -
> +  OneOfPagingEntry.Uint64          = 0;
>    //
>    // RegionLength: 256T (1 << 48) 512G (1 << 39), 1G (1 << 30), 2M (1 << 21)
> or 4K (1 << 12).
>    //
> @@ -367,8 +367,6 @@ PageTableLibMapInLevel (
>        if (RETURN_ERROR (Status)) {
>          return Status;
>        }
> -
> -      OneOfPagingEntry.Pnle.Uint64 = 0;
>      } else {
>        PageTableLibSetPle (Level, &OneOfPagingEntry, 0, &PleBAttribute,
> &AllOneMask);
>      }
> --
> 2.31.1.windows.1



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