linux-kernel - Re: [PATCH v17 02/26] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection

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Message-ID: <e249dad7-1a33-964c-ffa6-c7921564c813@intel.com>
Date:   Tue, 19 Jan 2021 10:10:24 -0800
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>
Subject: Re: [PATCH v17 02/26] x86/cet/shstk: Add Kconfig option for user-mode
 control-flow protection

On 1/19/2021 3:06 AM, Borislav Petkov wrote:
> On Tue, Dec 29, 2020 at 01:30:29PM -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_USER 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@...el.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 7b6dd10b162a..72cff400b9ae 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1950,6 +1950,28 @@ config X86_SGX
>>   
>>   	  If unsure, say N.
>>   
>> +config ARCH_HAS_SHADOW_STACK
>> +	def_bool n
>> +
>> +config X86_CET_USER
> 
> That thing needs to be X86_CET. How many times do I need to type this
> before you do it?
> 

Yes, I totally understand that now.  I was still thinking about 
separately enabling user/kernel mode.  Perhaps I should have 
communicated that thought before the change.  Sorry about that.  I will 
update it.

--
Yu-cheng