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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id s197sm20482307pfc.188.2020.06.24.08.45.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 08:45:48 -0700 (PDT) Date: Wed, 24 Jun 2020 08:45:47 -0700 From: Kees Cook To: Ard Biesheuvel Cc: Will Deacon , Fangrui Song , Catalin Marinas , Mark Rutland , Peter Collingbourne , James Morse , Borislav Petkov , Thomas Gleixner , Ingo Molnar , Russell King , Masahiro Yamada , Arvind Sankar , Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , X86 ML , clang-built-linux , linux-arch , linux-efi , Linux ARM , Linux Kernel Mailing List Subject: Re: [PATCH v3 3/9] efi/libstub: Remove .note.gnu.property Message-ID: <202006240844.7BE48D2B5@keescook> References: <20200624014940.1204448-1-keescook@chromium.org> <20200624014940.1204448-4-keescook@chromium.org> <20200624033142.cinvg6rbg252j46d@google.com> <202006232143.66828CD3@keescook> <20200624104356.GA6134@willie-the-truck> <202006240820.A3468F4@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 24, 2020 at 05:31:06PM +0200, Ard Biesheuvel wrote: > On Wed, 24 Jun 2020 at 17:21, Kees Cook wrote: > > > > On Wed, Jun 24, 2020 at 12:46:32PM +0200, Ard Biesheuvel wrote: > > > I'm not sure if there is a point to having PAC and/or BTI in the EFI > > > stub, given that it runs under the control of the firmware, with its > > > memory mappings and PAC configuration etc. > > > > Is BTI being ignored when the firmware runs? > > Given that it requires the 'guarded' attribute to be set in the page > tables, and the fact that the UEFI spec does not require it for > executables that it invokes, nor describes any means of annotating > such executables as having been built with BTI annotations, I think we > can safely assume that the EFI stub will execute with BTI disabled in > the foreseeable future. yaaaaaay. *sigh* How long until EFI catches up? That said, BTI shouldn't _hurt_, right? If EFI ever decides to enable it, we'll be ready? -- Kees Cook