Multiple SMM memory corruption vulnerabilities in SMM module on Gigabyte device (SMRAM write).

EFI_STATUS SwSmiHandler(
        EFI_HANDLE DispatchHandle,
        const void *Context,
        EFI_SMM_SW_CONTEXT *CommBuffer,
        UINTN *CommBufferSize)
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS NUMPAD "+" TO EXPAND]

  ...
  Value = 0;
  DataSize = 0x5F;
  Length = 0;
  Count = 0;
  Status = gEfiSmmVariableProtocol->SmmGetVariable(
             L"OcSetup",
             &OC_SETUP_VARIABLE_GUID,
             &Attributes,
             &DataSize,
             &OcSetupData);
  if ( Status < 0 || !OcSetupData.OverclockingSupport )
    return Status;
  if ( CommBuffer && CommBufferSize )
    CpuIndex = CommBuffer->SwSmiCpuIndex;
  if ( CpuIndex == -1 )
    return EFI_UNSUPPORTED;

  Status = gEfiSmmCpuProtocol->ReadSaveState(
             gEfiSmmCpuProtocol,
             4,
             EFI_SMM_SAVE_STATE_REGISTER_RBX,
             CpuIndex,
             &RbxRegister);

  Status = gEfiSmmCpuProtocol->ReadSaveState(gEfiSmmCpuProtocol, 4, EFI_SMM_SAVE_STATE_REGISTER_RCX, CpuIndex, &Buffer);

  BiosSettingHeader = RbxRegister;
  BiosSettingEntries = (RbxRegister + 16);

  TurboBoostEnabled = IsTurboBoostEnabled();
  ProgrammableTdpLimit = IsProgrammableTdpLimit();
  ProgrammableTjOffset = IsProgrammableTjOffset();

  if ( Buffer > 2 )
  {
    Value = 0x8004;
    Status0 = gEfiSmmCpuProtocol->WriteSaveState(
                gEfiSmmCpuProtocol,
                4,
                EFI_SMM_SAVE_STATE_REGISTER_RBX,
                CpuIndex,
                &Value);
    Status = Status0;
    return Status0;
  }
  if ( !Buffer )
  {
    Length = 0x110;
    Count = 0x20;
    if ( TurboBoostEnabled )
    {
      Length += 8;
      ++Count;
      if ( ProgrammableTdpLimit )
      {
        Length += 32;
        Count += 4;
      }
      if ( ProgrammableTjOffset )
      {
        Length += 16;
        Count += 2;
        if ( gCoreThreadCount > 2 )
        {
          Length += 16;
          Count += 2;
        }
      }
    }
    if ( BiosSettingHeader->Signature != '2DB$' )
    {
      if ( BiosSettingHeader->Signature == '$DB$' )
      {
        // SMRAM write
        BiosSettingHeader->Signature = '2DB$';
        BiosSettingHeader->Length = Length;
        BiosSettingHeader->MajorRev = 2;
        BiosSettingHeader->MinorRev = 0;

        Value = 1;
      }
      else
      {
        Value = 0x8001;
      }
      Status0 = gEfiSmmCpuProtocol->WriteSaveState(
                  gEfiSmmCpuProtocol,
                  4,
                  EFI_SMM_SAVE_STATE_REGISTER_RBX,
                  CpuIndex,
                  &Value);
      Status = Status0;
      return Status0;
    }
    if ( BiosSettingHeader->Length > 0xC00 )
    {
      Value = 0x8008;
      Status0 = gEfiSmmCpuProtocol->WriteSaveState(
                  gEfiSmmCpuProtocol,
                  4,
                  EFI_SMM_SAVE_STATE_REGISTER_RBX,
                  CpuIndex,
                  &Value);
      Status = Status0;
      return Status0;
    }
    if ( BiosSettingHeader->Length <= Length )
    {
      if ( BiosSettingHeader->Length < 0xC )
      {
        Value = 32771;
        Status0 = gEfiSmmCpuProtocol->WriteSaveState(
                    gEfiSmmCpuProtocol,
                    4,
                    EFI_SMM_SAVE_STATE_REGISTER_RBX,
                    CpuIndex,
                    &Value);
        Status = Status0;
        return Status0;
      }
      if ( BiosSettingHeader->Length < Length )
      {
        // SMRAM write
        BiosSettingHeader->Length = Length;
        BiosSettingHeader->MajorRev = 2;
        BiosSettingHeader->MinorRev = 0;

        Value = 32770;
        Status0 = gEfiSmmCpuProtocol->WriteSaveState(
                    gEfiSmmCpuProtocol,
                    4,
                    EFI_SMM_SAVE_STATE_REGISTER_RBX,
                    CpuIndex,
                    &Value);
        Status = Status0;
        return Status0;
      }
      Value = 0;
      Status = gEfiSmmCpuProtocol->WriteSaveState(
                 gEfiSmmCpuProtocol,
                 4u,
                 EFI_SMM_SAVE_STATE_REGISTER_RBX,
                 CpuIndex,
                 &Value);

      // SMRAM write
      BiosSettingHeader->MajorRev = 2;
      BiosSettingHeader->MinorRev = 0;
    }
    else
    {

      // SMRAM write
      BiosSettingHeader->Length = Length;
      BiosSettingHeader->MajorRev = 2;
      BiosSettingHeader->MinorRev = 0;

      Value = 2;
      Status = gEfiSmmCpuProtocol->WriteSaveState(
                 gEfiSmmCpuProtocol,
                 4,
                 EFI_SMM_SAVE_STATE_REGISTER_RBX,
                 CpuIndex,
                 &Value);
    }

    // SMRAM write
    BiosSettingHeader->Count = Count;

    // SMRAM write
    BiosSettingEntries->BiosImplementationType = 0x29;
    BiosSettingEntries->SettingValue = OcSetupData.EnableGv;
    BiosSettingEntries[1].BiosImplementationType = 0;
    BiosSettingEntries[1].SettingValue = OcSetupData.CpuRatio;
    BiosSettingEntries[2].BiosImplementationType = 7;
    BiosSettingEntries[2].SettingValue = OcSetupData.tCL;
    BiosSettingEntries[3].BiosImplementationType = 8;
    BiosSettingEntries[3].SettingValue = OcSetupData.tRCDtRP;
    BiosSettingEntries[4].BiosImplementationType = 0xA;
    BiosSettingEntries[4].SettingValue = OcSetupData.tRAS;
    BiosSettingEntries[5].BiosImplementationType = 0xB;
    if ( OcSetupData.tWR )
      BiosSettingEntries[5].SettingValue = OcSetupData.tWR;
    else
      BiosSettingEntries[5].SettingValue = 0xFFFFFFFE;
    BiosSettingEntries[6].BiosImplementationType = 0x15;
    BiosSettingEntries[6].SettingValue = OcSetupData.tRFC;
    BiosSettingEntries[7].BiosImplementationType = 0x16;
    BiosSettingEntries[7].SettingValue = OcSetupData.tRRD;
    BiosSettingEntries[8].BiosImplementationType = 0x17;
    BiosSettingEntries[8].SettingValue = OcSetupData.tWTR;
    BiosSettingEntries[9].BiosImplementationType = 0x19;
    BiosSettingEntries[9].SettingValue = OcSetupData.tRTP;
    BiosSettingEntries[10].BiosImplementationType = 0x28;
    BiosSettingEntries[10].SettingValue = OcSetupData.tFAW;
    BiosSettingEntries[11].BiosImplementationType = 0x18;
    if ( OcSetupData.NModeSupport )
      BiosSettingEntries[11].SettingValue = OcSetupData.NModeSupport;
    else
      BiosSettingEntries[11].SettingValue = 0xFFFFFFFE;
    ...
  }
  if...
  if...
  return Status;
}

// SMRAM write
BiosSettingHeader->Signature = '2DB$';
BiosSettingHeader->Length = Length;
BiosSettingHeader->MajorRev = 2;
BiosSettingHeader->MinorRev = 0;
...
// SMRAM write
BiosSettingHeader->Count = Count;

// SMRAM write
BiosSettingEntries->BiosImplementationType = 0x29;
BiosSettingEntries->SettingValue = OcSetupData.EnableGv;
BiosSettingEntries[1].BiosImplementationType = 0;
BiosSettingEntries[1].SettingValue = OcSetupData.CpuRatio;
BiosSettingEntries[2].BiosImplementationType = 7;
BiosSettingEntries[2].SettingValue = OcSetupData.tCL;
BiosSettingEntries[3].BiosImplementationType = 8;
BiosSettingEntries[3].SettingValue = OcSetupData.tRCDtRP;
BiosSettingEntries[4].BiosImplementationType = 0xA;
BiosSettingEntries[4].SettingValue = OcSetupData.tRAS;
BiosSettingEntries[5].BiosImplementationType = 0xB;
...