Date: Wed, 8 May 2019 12:02:39 -0700 From: Kees Cook <keescook@...omium.org> To: Alexander Potapenko <glider@...gle.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com>, Kees Cook <keescook@...omium.org>, Laura Abbott <labbott@...hat.com>, Linux-MM <linux-mm@...ck.org>, linux-security-module <linux-security-module@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Nick Desaulniers <ndesaulniers@...gle.com>, Kostya Serebryany <kcc@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Sandeep Patil <sspatil@...roid.com>, Randy Dunlap <rdunlap@...radead.org>, Jann Horn <jannh@...gle.com>, Mark Rutland <mark.rutland@....com> Subject: Re: [PATCH 1/4] mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options On Wed, May 8, 2019 at 8:38 AM Alexander Potapenko <glider@...gle.com> 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
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