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[209.85.217.44]) by smtp.gmail.com with ESMTPSA id x71sm971018vke.13.2019.05.08.12.02.51 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 08 May 2019 12:02:51 -0700 (PDT) Received: by mail-vs1-f44.google.com with SMTP id j184so13321302vsd.11 for ; Wed, 08 May 2019 12:02:51 -0700 (PDT) X-Received: by 2002:a67:f849:: with SMTP id b9mr15808201vsp.188.1557342170854; Wed, 08 May 2019 12:02:50 -0700 (PDT) MIME-Version: 1.0 References: <20190508153736.256401-1-glider@google.com> <20190508153736.256401-2-glider@google.com> In-Reply-To: <20190508153736.256401-2-glider@google.com> From: Kees Cook Date: Wed, 8 May 2019 12:02:39 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/4] mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options To: Alexander Potapenko Cc: Andrew Morton , Christoph Lameter , Kees Cook , Laura Abbott , Linux-MM , linux-security-module , Kernel Hardening , Masahiro Yamada , James Morris , "Serge E. Hallyn" , Nick Desaulniers , Kostya Serebryany , Dmitry Vyukov , Sandeep Patil , Randy Dunlap , Jann Horn , Mark Rutland Content-Type: text/plain; charset="UTF-8" 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 Wed, May 8, 2019 at 8:38 AM Alexander Potapenko wrote: > The new options are needed to prevent possible information leaks and > make control-flow bugs that depend on uninitialized values more > deterministic. I like having this available on both alloc and free. This makes it much more configurable for the end users who can adapt to their work loads, etc. > Linux build with -j12, init_on_free=1: +24.42% sys time (st.err 0.52%) > [...] > Linux build with -j12, init_on_alloc=1: +0.57% sys time (st.err 0.40%) Any idea why there is such a massive difference here? This seems to high just for cache-locality effects of touching all the freed pages. -- Kees Cook