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

["Kun Qin" <kuqin12@gmail.com>]

Hi SMM maintainers,

A gentle ping on this. Could you please provide some feedback on the fix 
below for allocating 0 sized pool when heap guard it on?

Thanks in advance,
Kun

On 3/28/2022 2:57 PM, Kun Qin wrote:
> Thanks, Liming.
>
> SMM owners/authors,
>
> Could you please also review the original issue and this patch to 
> provide feedback?
>
> Thanks,
> Kun
>
> On 3/17/2022 6:20 PM, gaoliming wrote:
>> Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
>>
>>> -----邮件原件-----
>>> 发件人: devel@edk2.groups.io <devel@edk2.groups.io> 代表 Kun Qin
>>> 发送时间: 2022年3月16日 12:00
>>> 收件人: devel@edk2.groups.io
>>> 抄送: Jiewen Yao <jiewen.yao@intel.com>; Eric Dong 
>>> <eric.dong@intel.com>;
>>> Ray Ni <ray.ni@intel.com>; Jian J Wang <jian.j.wang@intel.com>; 
>>> Liming Gao
>>> <gaoliming@byosoft.com.cn>
>>> 主题: [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
>>>
>>>
>>>
>>> 
>>>
>>
>>