Re: [PATCH] UefiCpuPkg/CommonFeature: Always set FEATURE_CONTROL.Lock

[Laszlo Ersek <lersek@redhat.com>]

Hello Ray,

On 11/13/18 08:35, Ruiyu Ni wrote:
> The patch reverts commit 1ed6498c4a0210204bf4b95cc0c0cd6623ad6a0b
> * UefiCpuPkg/CommonFeature: Skip locking when the feature is disabled
> 
> FEATURE_CONTROL.Lock bit is controlled by feature
> CPU_FEATURE_LOCK_FEATURE_CONTROL_REGISTER. The commit 1ed649 fixes
> a bug that when the feature is disabled, the Lock bit is cleared.
> But it's a security hole if the bit is cleared when booting OS.
> We can argue that platform needs to make sure the value
> of PcdCpuFeaturesUserConfiguration should be set properly to make
> sure feature CPU_FEATURE_LOCK_FEATURE_CONTROL_REGISTER is enabled.
> 
> But it's better to guarantee this in the generic core code.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Andrew Fish <afish@apple.com>
> Cc: Leif Lindholm <leif.lindholm@linaro.org>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> ---
>  UefiCpuPkg/Library/CpuCommonFeaturesLib/FeatureControl.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/FeatureControl.c b/UefiCpuPkg/Library/CpuCommonFeaturesLib/FeatureControl.c
> index 631c836857..8c1eb5eb4f 100644
> --- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/FeatureControl.c
> +++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/FeatureControl.c
> @@ -1,7 +1,7 @@
>  /** @file
>    Features in MSR_IA32_FEATURE_CONTROL register.
>  
> -  Copyright (c) 2017 - 2018, Intel Corporation. All rights reserved.<BR>
> +  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
>    This program and the accompanying materials
>    are licensed and made available under the terms and conditions of the BSD License
>    which accompanies this distribution.  The full text of the license may be found at
> @@ -184,15 +184,6 @@ LockFeatureControlRegisterInitialize (
>  {
>    MSR_IA32_FEATURE_CONTROL_REGISTER    *MsrRegister;
>  
> -  //
> -  // When Lock Feature Control Register feature is disabled,
> -  // just skip the MSR lock bit setting.
> -  // The MSR lock bit is cleared by default and write-once in a boot.
> -  //
> -  if (!State) {
> -    return RETURN_SUCCESS;
> -  }
> -
>    //
>    // The scope of Lock bit in the MSR_IA32_FEATURE_CONTROL is core for
>    // below processor type, only program MSR_IA32_FEATURE_CONTROL for thread 0 in each
> 

(1) The following TianoCore BZ:

  https://bugzilla.tianocore.org/show_bug.cgi?id=1305

is in status RESOLVED|FIXED.

When you push this patch:

- please re-open BZ#1305,
- record the commit hash of this patch in BZ#1305.

(2) Please reference BZ#1305 in the commit message.

(3) Eric should provide an R-b for this revert, before you push it. My
current comments are not sufficient for that.

--*--

For the file "UefiCpuPkg/Library/CpuCommonFeaturesLib/FeatureControl.c",
there have been no further commits since 1ed6498c4a02 (with master being
at da2c81ee96eb now), so this looks like a proper revert.

And, assuming your assessment of the security impact is correct, I agree
this revert should be pushed, before we apply the edk2-stable201811 tag.

With (1) through (3) addressed:

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks,
Laszlo