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([2600:1010:b04b:3f76:e5b1:55a0:5bce:dce3]) by smtp.gmail.com with ESMTPSA id y10sm9771144pff.197.2021.01.29.11.58.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 Jan 2021 11:58:23 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v18 02/25] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection Date: Fri, 29 Jan 2021 11:58:21 -0800 Message-Id: <86F8CE62-A94B-46BD-9A29-DBE1CC14AA83@amacapital.net> References: <40a5a9b5-9c83-473d-5f62-a16ecde50f2a@intel.com> Cc: Yu-cheng Yu , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , 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 , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu In-Reply-To: <40a5a9b5-9c83-473d-5f62-a16ecde50f2a@intel.com> To: Dave Hansen X-Mailer: iPhone Mail (18C66) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Jan 29, 2021, at 11:42 AM, Dave Hansen wrote: >=20 > =EF=BB=BFOn 1/27/21 1:25 PM, Yu-cheng Yu wrote: >> + help >> + Control-flow protection is a hardware security hardening feature >> + that detects function-return address or jump target changes by >> + malicious code. >=20 > It's not really one feature. I also think it's not worth talking about > shadow stacks or indirect branch tracking in *here*. Leave that for > Documentation/. >=20 > Just say: >=20 > Control-flow protection is a set of hardware features which > place additional restrictions on indirect branches. These help > mitigate ROP attacks. >=20 > ... and add more in the IBT patches. >=20 >> Applications must be enabled to use it, and old >> + userspace does not get protection "for free". >> + Support for this feature is present on processors released in >> + 2020 or later. Enabling this feature increases kernel text size >> + by 3.7 KB. >=20 > Did any CPUs ever get released that have this? If so, name them. If > not, time to change this to 2021, I think. Zen 3 :)=