[edk2-devel] [RFC] MemoryProtectionLib for Dynamic Memory Guard Settings

[Taylor Beebe]

Thanks for your feedback, Jian.

In option 2, a most basic implementation would returning the current 
FixedAtBuild PCDs assuming they are kept. If they aren't, the library 
implementer could simply hard-code the return value for each memory 
protection setting.

In option 1, the HOB would be published in pre-mem and I'm not an expert 
on exploiting the pre-mem environment. Jiewen may have more to say on this.

-Taylor

On 7/28/2021 7:18 PM, Wang, Jian J wrote:
> Thanks for the RFC. I'm not object to this idea. The only concern from me
> is the potential security holes introduced by the changes. According to your
> description, it allows 3rd party software to violate memory protection policy.
> I'd like to see more explanations on how to avoid it to be exploited.
> 
> +Jiewen, what's current process to evaluate the security threat?
> 
> Regards,
> Jian
> 
>> -----Original Message-----
>> From: Taylor Beebe <t at taylorbeebe.com>
>> Sent: Friday, July 23, 2021 8:33 AM
>> To: devel at edk2.groups.io
>> Cc: spbrogan at outlook.com; Dong, Eric <eric.dong at intel.com>; Ni, Ray
>> <ray.ni at intel.com>; Kumar, Rahul1 <Rahul1.Kumar at intel.com>;
>> mikuback at linux.microsoft.com; Wang, Jian J <jian.j.wang at intel.com>; Wu,
>> Hao A <hao.a.wu at intel.com>; Bi, Dandan <dandan.bi at intel.com>;
>> gaoliming at byosoft.com.cn; Dong, Guo <guo.dong at intel.com>; Ma, Maurice
>> <maurice.ma at intel.com>; You, Benjamin <benjamin.you at intel.com>
>> Subject: [RFC] MemoryProtectionLib for Dynamic Memory Guard Settings
>>
>> Current memory protection settings rely on FixedAtBuild PCD values
>> (minus PcdSetNxForStack). Because of this, the memory protection
>> configuration interface is fixed in nature. Cases arise in which memory
>> protections might need to be adjusted between boots (if platform design
>> allows) to avoid disabling a system. For example, platforms might choose
>> to allow the user to control their protection policies such as allow
>> execution of critical 3rd party software that might violate memory
>> protections.
>>
>> This RFC seeks your feedback regarding introducing an interface that
>> allows dynamic configuration of memory protection settings.
>>
>> I would like to propose two options:
>> 1. Describing the memory protection setting configuration in a HOB that
>> is produced by the platform.
>> 2. Introducing a library class (e.g. MemoryProtectionLib) that allows
>> abstraction of the memory protection setting configuration data source.
>>
>> In addition, I would like to know if the memory protection FixedAtBuild
>> PCDs currently in MdeModulePkg can be removed so we can move the
>> configuration interface entirely to an option above.
>>
>> In any case, I would like the settings to be visible to environments
>> such as Standalone MM where dynamic PCDs are not accessible.
>>
>> I am seeking your feedback on this proposal in preparation for sending
>> an edk2 patch series.
>>
>> --
>> Taylor Beebe
>> Software Engineer @ Microsoft

-- 
Taylor Beebe
Software Engineer @ Microsoft


-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#78386): https://edk2.groups.io/g/devel/message/78386
Mute This Topic: https://groups.io/mt/84392478/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-