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

From: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>
Subject: Re: [PATCH v17 02/26] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection
Date: Tue, 19 Jan 2021 10:10:24 -0800	[thread overview]
Message-ID: <e249dad7-1a33-964c-ffa6-c7921564c813@intel.com> (raw)
In-Reply-To: <20210119110659.GG27433@zn.tnic>

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@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 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