Re: [edk2-devel] [PATCH v1 1/1] MdeModulePkg: PiSmmCore: Inspect memory guarded with pool headers

["Wang, Jian J" <jian.j.wang@intel.com>]

It looks good to me. Thanks for fixing it.

Reviewed-by: Jian J Wang <jian.j.wang@intel.com>

Regards,
Jian

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Kun Qin
> Sent: Wednesday, March 16, 2022 12:00 PM
> To: devel@edk2.groups.io
> Cc: Yao, Jiewen <jiewen.yao@intel.com>; Dong, Eric <eric.dong@intel.com>; Ni,
> Ray <ray.ni@intel.com>; Wang, Jian J <jian.j.wang@intel.com>; Gao, Liming
> <gaoliming@byosoft.com.cn>
> Subject: [edk2-devel] [PATCH v1 1/1] MdeModulePkg: PiSmmCore: Inspect
> memory guarded with pool headers
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3488
> 
> Current free pool routine from PiSmmCore will inspect memory guard status
> for target buffer without considering pool headers. This could lead to
> `IsMemoryGuarded` function to return incorrect results.
> 
> In that sense, allocating a 0 sized pool could cause an allocated buffer
> directly points into a guard page, which is legal. However, trying to
> free this pool will cause the routine changed in this commit to read XP
> pages, which leads to page fault.
> 
> This change will inspect memory guarded with pool headers. This can avoid
> errors when a pool content happens to be on a page boundary.
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> 
> Signed-off-by: Kun Qin <kuqin12@gmail.com>
> ---
>  MdeModulePkg/Core/PiSmmCore/Pool.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/MdeModulePkg/Core/PiSmmCore/Pool.c
> b/MdeModulePkg/Core/PiSmmCore/Pool.c
> index 96ebe811c669..e1ff40a8ea55 100644
> --- a/MdeModulePkg/Core/PiSmmCore/Pool.c
> +++ b/MdeModulePkg/Core/PiSmmCore/Pool.c
> @@ -382,11 +382,6 @@ SmmInternalFreePool (
>      return EFI_INVALID_PARAMETER;
>    }
> 
> -  MemoryGuarded = IsHeapGuardEnabled () &&
> -                  IsMemoryGuarded ((EFI_PHYSICAL_ADDRESS)(UINTN)Buffer);
> -  HasPoolTail = !(MemoryGuarded &&
> -                  ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) == 0));
> -
>    FreePoolHdr = (FREE_POOL_HEADER *)((POOL_HEADER *)Buffer - 1);
>    ASSERT (FreePoolHdr->Header.Signature == POOL_HEAD_SIGNATURE);
>    ASSERT (!FreePoolHdr->Header.Available);
> @@ -394,6 +389,11 @@ SmmInternalFreePool (
>      return EFI_INVALID_PARAMETER;
>    }
> 
> +  MemoryGuarded = IsHeapGuardEnabled () &&
> +                  IsMemoryGuarded ((EFI_PHYSICAL_ADDRESS)(UINTN)FreePoolHdr);
> +  HasPoolTail = !(MemoryGuarded &&
> +                  ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) == 0));
> +
>    if (HasPoolTail) {
>      PoolTail = HEAD_TO_TAIL (&FreePoolHdr->Header);
>      ASSERT (PoolTail->Signature == POOL_TAIL_SIGNATURE);
> --
> 2.35.1.windows.2
> 
> 
> 
> 
>