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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b5-20020a62cf05000000b005821db4fd84sm12268781pfg.131.2023.01.19.17.01.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Jan 2023 17:01:58 -0800 (PST) Date: Thu, 19 Jan 2023 17:01:57 -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 Subject: Re: [PATCH v5 25/39] mm: Warn on shadow stack memory in wrong vma Message-ID: <202301191701.A8201D9C@keescook> References: <20230119212317.8324-1-rick.p.edgecombe@intel.com> <20230119212317.8324-26-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230119212317.8324-26-rick.p.edgecombe@intel.com> X-Stat-Signature: 97u9z1ypr91a67cjhb1bw8g7akr9mnko X-Rspam-User: X-Rspamd-Queue-Id: 0516B2000F X-Rspamd-Server: rspam06 X-HE-Tag: 1674176519-771571 X-HE-Meta: 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 wZGnwf// 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 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 Thu, Jan 19, 2023 at 01:23:03PM -0800, Rick Edgecombe wrote: > The x86 Control-flow Enforcement Technology (CET) feature includes a new > type of memory called shadow stack. This shadow stack memory has some > unusual properties, which requires some core mm changes to function > properly. > > One sharp edge is that PTEs that are both Write=0 and Dirty=1 are > treated as shadow by the CPU, but this combination used to be created by > the kernel on x86. Previous patches have changed the kernel to now avoid > creating these PTEs unless they are for shadow stack memory. In case any > missed corners of the kernel are still creating PTEs like this for > non-shadow stack memory, and to catch any re-introductions of the logic, > warn if any shadow stack PTEs (Write=0, Dirty=1) are found in non-shadow > stack VMAs when they are being zapped. This won't catch transient cases > but should have decent coverage. It will be compiled out when shadow > stack is not configured. > > In order to check if a pte is shadow stack in core mm code, add default > implementations for pte_shstk() and pmd_shstk(). > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Rick Edgecombe Reviewed-by: Kees Cook -- Kees Cook