Re: [PATCH v19 02/25] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection

Yu, Yu-cheng
2021-02-05T00:05:12Z

On 2/4/2021 11:56 AM, Kees Cook wrote:
> On Wed, Feb 03, 2021 at 02:55:24PM -0800, Yu-cheng Yu wrote:
>> Shadow Stack provides protection against function return address
>> corruption. It is active when the processor supports it, the kernel has
>> CONFIG_X86_CET enabled, and the application is built for the feature.
>> This is only implemented for the 64-bit kernel. When it is enabled, legacy
>> non-Shadow Stack applications continue to work, but without protection.
>>
>> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
>> ---
>> arch/x86/Kconfig | 22 ++++++++++++++++++++++
>> arch/x86/Kconfig.assembler | 5 +++++
>> 2 files changed, 27 insertions(+)
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index 21f851179ff0..074b3c0e6bf6 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1951,6 +1951,28 @@ config X86_SGX
>>
>> If unsure, say N.
>>
>> +config ARCH_HAS_SHADOW_STACK
>> + def_bool n
>> +
>> +config X86_CET
>> + prompt "Intel Control-flow protection for user-mode"
>> + def_bool n
>> + depends on X86_64
>> + depends on AS_WRUSS
>> + select ARCH_USES_HIGH_VMA_FLAGS
>> + select ARCH_HAS_SHADOW_STACK
>
> This seems backwards to me? Shouldn't 'config X86_64' do the 'select
> ARCH_HAS_SHADOW_STACK' and 'config X86_CET' do a 'depends on
> ARCH_HAS_SHADOW_STACK' instead?

I will change it. Thanks!

--
Yu-cheng