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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id y14-20020a62640e000000b0056bb4bbfb9bsm2971706pfb.95.2022.12.02.18.31.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Dec 2022 18:31:44 -0800 (PST) Date: Fri, 2 Dec 2022 18:31:43 -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 11/39] x86/mm: Update pte_modify for _PAGE_COW Message-ID: <202212021831.697AA89B7B@keescook> References: <20221203003606.6838-1-rick.p.edgecombe@intel.com> <20221203003606.6838-12-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221203003606.6838-12-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C05A8C000C X-Stat-Signature: 4ci79zbpuffh4ddjghwnoteeyffrs96g X-Spamd-Result: default: False [6.08 / 9.00]; SORBS_IRL_BL(3.00)[209.85.215.174:from]; SUSPICIOUS_RECIPS(1.50)[]; SUBJECT_HAS_UNDERSCORES(1.00)[]; MID_RHS_NOT_FQDN(0.50)[]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; BAYES_HAM(-0.02)[48.25%]; ARC_NA(0.00)[]; TAGGED_RCPT(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_ALLOW(0.00)[chromium.org:s=google]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[39]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; 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]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; DKIM_TRACE(0.00)[chromium.org:+]; TO_DN_SOME(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; FROM_HAS_DN(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[] X-HE-Tag: 1670034705-673610 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 04:35:38PM -0800, Rick Edgecombe wrote: > From: Yu-cheng Yu > > The Write=0,Dirty=1 PTE has been used to indicate copy-on-write pages. > However, newer x86 processors also regard a Write=0,Dirty=1 PTE as a > shadow stack page. In order to separate the two, the software-defined > _PAGE_DIRTY is changed to _PAGE_COW for the copy-on-write case, and > pte_*() are updated to do this. > > pte_modify() takes a "raw" pgprot_t which was not necessarily created > with any of the existing PTE bit helpers. That means that it can return a > pte_t with Write=0,Dirty=1, a shadow stack PTE, when it did not intend to > create one. > > However pte_modify() changes a PTE to 'newprot', but it doesn't use the > pte_*(). Modify it to also move _PAGE_DIRTY to _PAGE_COW. Apply the same > changes to pmd_modify(). > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook -- Kees Cook