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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id h4-20020aa79f44000000b0056d7cc80ea4sm10783612pfr.110.2023.01.19.17.01.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Jan 2023 17:01:19 -0800 (PST) Date: Thu, 19 Jan 2023 17:01:18 -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 v5 19/39] mm: Fixup places that call pte_mkwrite() directly Message-ID: <202301191701.ADBD82708A@keescook> References: <20230119212317.8324-1-rick.p.edgecombe@intel.com> <20230119212317.8324-20-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230119212317.8324-20-rick.p.edgecombe@intel.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C84D14001C X-Stat-Signature: 1ixbbtp7k8cm57zkbq1nb39bk4tis6o5 X-Rspam-User: X-HE-Tag: 1674176480-407558 X-HE-Meta: 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 mvT2MXps gSsOHdR8acCvlcIylkdfr2iXptJjp0VwZtVYpF+r8XdCOgrWhKYhLe3c0/9K5LZpFDDVIe7N8PFGQ6OfV8p4vm4ho4pVj2ZLff9673eMwC3fKSmkvFbOC5AbPQyqkQ3vGEpzIxUOPFAaR2Jxg6PswTEQSZ2LPUqLhJse33aN7gunbZDeatx0ibM5PGfqcIcggCdPv9d2S1sD2ndAK3q4MAfC0Ym4Zb9Lgd7bYsLOtvyBMYViM/FkVmpGkkd4Xi691ZhX1LziUVSgwK8u/nsCtIKKAjRj+flINB2ON3OT6VFm94NSGU4z8bPwICOMJTCcAH+uG2bC58/rq5kKDbgORdozi3Sf4NH3hdaNE9qlmnys5GdOuoEM1rBoFd43PrbjcKaiTCk0lDIUT1A3MfrtIFDH8OGvfg9qhPlzhqDZKZNIPV1s0pIEkz83BlF/1avKi2O/N4m2EBUPxoTISHnan9HyI44bnrbYRHC401EM3VEYRcEAs5UOICerW4shraIwjdlV8aVVNUjpnOoKz6T6e5SkCf1MdSKi5JzPT3Dnz3c64J1wW38Sb/lOliOhJGEZ9UsQghzS/rjzjqF/KHn7zZcKnzg== 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 01:22:57PM -0800, Rick Edgecombe wrote: > From: Yu-cheng Yu > > 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. > > With the introduction of shadow stack memory there are two ways a pte can > be writable: regular writable memory and shadow stack memory. > > In past patches, maybe_mkwrite() has been updated to apply pte_mkwrite() > or pte_mkwrite_shstk() depending on the VMA flag. This covers most cases > where a PTE is made writable. However, there are places where pte_mkwrite() > is called directly and the logic should now also create a shadow stack PTE > in the case of a shadow stack VMA. > > - do_anonymous_page() and migrate_vma_insert_page() check VM_WRITE > directly and call pte_mkwrite(). Teach it about pte_mkwrite_shstk() > > - When userfaultfd is creating a PTE after userspace handles the fault > it calls pte_mkwrite() directly. Teach it about pte_mkwrite_shstk() > > To make the code cleaner, introduce is_shstk_write() which simplifies > checking for VM_WRITE | VM_SHADOW_STACK together. > > In other cases where pte_mkwrite() is called directly, the VMA will not > be VM_SHADOW_STACK, and so shadow stack memory should not be created. > - In the case of pte_savedwrite(), shadow stack VMA's are excluded. > - In the case of the "dirty_accountable" optimization in mprotect(), > shadow stack VMA's won't be VM_SHARED, so it is not necessary. > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook -- Kees Cook