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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z68sm2866767pgz.88.2019.08.29.09.25.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2019 09:25:33 -0700 (PDT) Date: Thu, 29 Aug 2019 09:25:32 -0700 From: Kees Cook To: "Theodore Y. Ts'o" , Hsin-Yi Wang , Stephen Boyd , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , Russell King , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , "Paul E . McKenney" , Kate Stewart , "David S . Miller" , Viresh Kumar , Marek Szyprowski , Arnd Bergmann , Marc Zyngier , Julien Thierry , Greg Kroah-Hartman , Wei Li , Anders Roxell , Rob Herring , Aaro Koskinen , Daniel Thompson , Tim Chen , Rik van Riel , Waiman Long , Marcelo Tosatti , Peter Zijlstra , Armijn Hemel , Grzegorz Halat , Len Brown , Shaokun Zhang , Mike Rapoport , Guenter Roeck , Andrew Morton , Mathieu Desnoyers , Alexey Dobriyan , Yury Norov , Josh Poimboeuf , Jiri Kosina , Mukesh Ojha , lkml Subject: Re: [PATCH v9 2/3] fdt: add support for rng-seed Message-ID: <201908290922.5C6E4885D@keescook> References: <20190822071522.143986-1-hsinyi@chromium.org> <20190822071522.143986-3-hsinyi@chromium.org> <5d5ed368.1c69fb81.419fc.0803@mx.google.com> <201908241203.92CC0BE8@keescook> <20190829154505.GB10779@mit.edu> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190829154505.GB10779@mit.edu> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190829_092535_274811_2B759D9D X-CRM114-Status: GOOD ( 19.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Aug 29, 2019 at 11:45:05AM -0400, Theodore Y. Ts'o wrote: > I thought about asking for this, but we really want to do this as > early as possible, so that it can be used by KASLR and other services KASLR entropy is sent via a separate DT entry, since it's needed before the kernel is even running. > that are run super early. Also, whether or not we can trust the Are there things using the kernel RNG before the stack canary is set up? I tried to move all of that code as early as possible already. > bootloader is going to be a system-level thing. This should probably > be defaulted to off, and only enabled by the system integrator if they > are 100%, positively sure, that the entire system is one where we can > trust the source of randomness which the bootloader is using --- or > for that matter, that the bootloader is trustworthy! > > Is it really going to be that useful for a random system administrator > to be able to flip this on or off from the command line? Hopefully > there will be an easy way to configure the firmware or the bootloader > to simply not supply entropy, if for some reason it's not trustworthy. You have a point about bootloader vs system design. I'm cautiously convinced we don't need a boot param, but if we CAN put all the entropy collection in a single place, that'd be nice. -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel