Re: [edk2-devel] [PATCH v1 1/1] UefiCpuPkg: PiSmmCpuDxeSmm: Check buffer size before accessing

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

Hi Laszlo,

Thanks for the feedback. I will update the description in v2.

Regards,
Kun

On 04/06/2021 05:09, Laszlo Ersek wrote:
> On 03/27/21 00:41, Kun Qin wrote:
>> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3283
>>
>> Current SMM Save State routine does not check the number of bytes to be
>> read, when it comse to read IO_INFO, before casting the incoming buffer
>> to EFI_SMM_SAVE_STATE_IO_INFO. This could potentially cause memory
>> corruption due to extra bytes are written out of buffer boundary.
>>
>> This change adds a width check before copying IoInfo into output buffer.
>>
>> Cc: Eric Dong <eric.dong@intel.com>
>> Cc: Ray Ni <ray.ni@intel.com>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Rahul Kumar <rahul1.kumar@intel.com>
>>
>> Signed-off-by: Kun Qin <kuqin12@gmail.com>
>> ---
>>   UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c b/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c
>> index 661cc51f361a..ec760e4c37ca 100644
>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c
>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c
>> @@ -418,6 +418,13 @@ ReadSaveStateRegister (
>>         return EFI_NOT_FOUND;
>>       }
>>   
>> +    //
>> +    // Make sure the incoming buffer is large enough to hold IoInfo before accessing
>> +    //
>> +    if (Width < sizeof (EFI_SMM_SAVE_STATE_IO_INFO)) {
>> +      return EFI_INVALID_PARAMETER;
>> +    }
>> +
>>       //
>>       // Zero the IoInfo structure that will be returned in Buffer
>>       //
>>
> 
> Please update the description of the EFI_INVALID_PARAMETER return code
> in the function's leading comment as well.
> 
> With that:
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> 
> Thanks
> Laszlo
>