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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id l12-20020a170902e2cc00b00176a6ba5969sm439650plc.98.2022.12.02.18.35.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Dec 2022 18:35:00 -0800 (PST) Date: Fri, 2 Dec 2022 18:34:59 -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 17/39] x86/mm: Update maybe_mkwrite() for shadow stack Message-ID: <202212021834.200AFA92BC@keescook> References: <20221203003606.6838-1-rick.p.edgecombe@intel.com> <20221203003606.6838-18-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221203003606.6838-18-rick.p.edgecombe@intel.com> X-Spamd-Result: default: False [5.83 / 9.00]; SORBS_IRL_BL(3.00)[209.85.216.43:from]; SUSPICIOUS_RECIPS(1.50)[]; SUBJECT_HAS_UNDERSCORES(1.00)[]; MID_RHS_NOT_FQDN(0.50)[]; BAYES_HAM(-0.27)[67.73%]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_TWELVE(0.00)[39]; ARC_NA(0.00)[]; R_DKIM_ALLOW(0.00)[chromium.org:s=google]; MIME_TRACE(0.00)[0:+]; TAGGED_RCPT(0.00)[]; DMARC_POLICY_ALLOW(0.00)[chromium.org,none]; TO_MATCH_ENVRCPT_SOME(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; DKIM_TRACE(0.00)[chromium.org:+]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; RCVD_COUNT_THREE(0.00)[3]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[] X-Rspamd-Queue-Id: 028562000B X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: n73wpdxuh5ic3j1iuddrmmwniin913yj X-HE-Tag: 1670034901-208757 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 04:35:44PM -0800, Rick Edgecombe wrote: > From: Yu-cheng Yu > > When serving a page fault, maybe_mkwrite() makes a PTE writable if there is > a write access to it, and its vma has VM_WRITE. Shadow stack accesses to > shadow stack vma's are also treated as write accesses by the fault handler. > This is because setting shadow stack memory makes it writable via some > instructions, so COW has to happen even for shadow stack reads. > > So maybe_mkwrite() should continue to set VM_WRITE vma's as normally > writable, but also set VM_WRITE|VM_SHADOW_STACK vma's as shadow stack. > > Do this by adding a pte_mkwrite_shstk() and a cross-arch stub. Check for > VM_SHADOW_STACK in maybe_mkwrite() and call pte_mkwrite_shstk() > accordingly. > > Apply the same changes to maybe_pmd_mkwrite(). > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook -- Kees Cook