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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 , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , 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, david@redhat.com, debug@rivosinc.com Subject: Re: [PATCH v7 24/41] mm: Don't allow write GUPs to shadow stack memory Message-ID: References: <20230227222957.24501-1-rick.p.edgecombe@intel.com> <20230227222957.24501-25-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230227222957.24501-25-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 69E4720026 X-Stat-Signature: hm9mzxkpofud7madw98rui7wogehh61f X-HE-Tag: 1678108219-686309 X-HE-Meta: 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 rpe4Ok/C Bg85i1y8a0V5a8y6+ci7NfVxaH3Q9SmQMIN2RWfhMpJ+7SN9Th74s91NAiwHpTnRQLH/u++BcYdC1ACHfP3bXhiRkAIo9SmDcrpTSb4MDhqnPdC3nqRK0Xgf9u7kQB3iFtwCLQ+EiYXpJlCcQOuAKRBo2dQGNJaYlYONKeV+SJV0XUAYwNQPAjlxN/+M1Lqsyhu5Mf3miMuGkSY6yyucPVt/ynx1cNRm2y4h5E+hPFYQjgJVWMp1IHJZCDsFkPKmWMa7WIvxhanPTR0mCNBozvGNfrQ== 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 Mon, Feb 27, 2023 at 02:29:40PM -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. > > Shadow stack memory is writable only in very specific, controlled ways. > However, since it is writable, the kernel treats it as such. As a result ^ , > there remain many ways for userspace to trigger the kernel to write to > shadow stack's via get_user_pages(, FOLL_WRITE) operations. To make this a "stacks" or "to write to a shadow stack via..." > little less exposed, block writable GUPs for shadow stack VMAs. GUPs? I supposed this means "prevent get_user_pages() from pinning pages to which the corresponding VMA is a shadow stack one."? Or something like that which is less mm-internal speak... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette