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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id y1-20020aa79421000000b005765a5ff1fasm2124160pfo.213.2022.12.02.18.23.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Dec 2022 18:23:17 -0800 (PST) Date: Fri, 2 Dec 2022 18:23:16 -0800 From: Kees Cook To: Rick Edgecombe Cc: 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 , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, Yu-cheng Yu Subject: Re: [PATCH v4 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack Message-ID: <202212021823.81E4669@keescook> References: <20221203003606.6838-1-rick.p.edgecombe@intel.com> <20221203003606.6838-5-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221203003606.6838-5-rick.p.edgecombe@intel.com> X-Rspam-User: X-Spamd-Result: default: False [2.96 / 9.00]; SORBS_IRL_BL(3.00)[209.85.216.52:from]; BAYES_HAM(-2.14)[87.91%]; SUSPICIOUS_RECIPS(1.50)[]; MID_RHS_NOT_FQDN(0.50)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; RCVD_NO_TLS_LAST(0.10)[]; DKIM_TRACE(0.00)[chromium.org:+]; RCPT_COUNT_TWELVE(0.00)[39]; FROM_EQ_ENVFROM(0.00)[]; DMARC_POLICY_ALLOW(0.00)[chromium.org,none]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; R_DKIM_ALLOW(0.00)[chromium.org:s=google]; ARC_NA(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; FROM_HAS_DN(0.00)[]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; TO_DN_SOME(0.00)[]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[] X-Rspamd-Queue-Id: 45DB98000F X-Rspamd-Server: rspam01 X-Stat-Signature: ejd53wx1ana3ujfgfxoohqtnjgu13mas X-HE-Tag: 1670034199-819577 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 Fri, Dec 02, 2022 at 04:35:31PM -0800, Rick Edgecombe wrote: > From: Yu-cheng Yu > > Setting CR4.CET is a prerequisite for utilizing any CET features, most of > which also require setting MSRs. > > Kernel IBT already enables the CET CR4 bit when it detects IBT HW support > and is configured with kernel IBT. However, future patches that enable > userspace shadow stack support will need the bit set as well. So change > the logic to enable it in either case. > > Clear MSR_IA32_U_CET in cet_disable() so that it can't live to see > userspace in a new kexec-ed kernel that has CR4.CET set from kernel IBT. > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook -- Kees Cook