Re: [edk2-devel] [PATCH v1 0/2] MM communicate functionality in variable policy

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

Hi ArmPkg and MdeModulePkg maintainers,

It has been a week since the patches were sent. Could you please review 
the changes and let me know if there is any feedback? Any input is 
appreciated.

Regards,
Kun

On 11/29/2021 16:39, Kun Qin via groups.io wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3709
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3751
> 
> Currently, setups with variable policy operations used together with MM
> communicate from ArmPkg could fail with `EFI_INVALID_PARAMETER`. This was
> due to the errors from 2 following aspects:
> 
> 1. For variable policy implementations in MdeModulePkg, the DXE runtime
> agent would communicate to MM to disable, register or query policies.
> However, during these operations, the MessageLength calculation is
> including MM communicate header. This could lead to MM agent read data
> across the given buffer boundary and/or trigger other errors.
> 
> 2. On the other hand, current MM communicate routine from ArmPkg would
> fail the function if the input message length does not equal to input
> buffer size.
> 
> As defined in PI specification, the `CommSize`, when as input, should
> stand for "The size of the data buffer being passed in", which would mean
> the maximal number of bytes `CommBuffer` can hold. In turn, the value of
> this input parameter can be used for MM handlers to determine whether the
> output data is too large to fit in this buffer. Enforcing the incoming
> buffer to hold exactly the number of used bytes mismatches with the PI
> spec description.
> 
> This change fix MessageLength field calculation from variable policy and
> updated input argument inspections from MM communicate routine in ArmPkg
> to match PI spec descriptions.
> 
> Patch v1 branch: https://github.com/kuqin12/edk2/tree/mm_communicate_check
> 
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Leif Lindholm <leif@nuviainc.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
> Cc: Michael Kubacki <michael.kubacki@microsoft.com>
> 
> Kun Qin (2):
>    MdeModulePkg: VariableSmmRuntimeDxe: Fix Variable Policy Message
>      Length
>    ArmPkg: MmCommunicationDxe: Update MM communicate input arguments
>      checks
> 
>   ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c               | 44 ++++++++++++--------
>   MdeModulePkg/Universal/Variable/RuntimeDxe/VariablePolicySmmDxe.c | 10 ++---
>   2 files changed, 32 insertions(+), 22 deletions(-)
>