Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755891AbbKYAoM (ORCPT ); Tue, 24 Nov 2015 19:44:12 -0500 Received: from mail-ig0-f173.google.com ([209.85.213.173]:36565 "EHLO mail-ig0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752871AbbKYAoJ (ORCPT ); Tue, 24 Nov 2015 19:44:09 -0500 MIME-Version: 1.0 In-Reply-To: References: <1448401114-24650-1-git-send-email-keescook@chromium.org> <1448401114-24650-2-git-send-email-keescook@chromium.org> Date: Tue, 24 Nov 2015 16:44:07 -0800 X-Google-Sender-Auth: olelTQtCZybt0T6ESlQ41SnU_68 Message-ID: Subject: Re: [PATCH 1/2] x86: introduce post-init read-only memory From: Kees Cook To: Andy Lutomirski Cc: linux-arch , Thomas Gleixner , Ingo Molnar , "linux-kernel@vger.kernel.org" , "kernel-hardening@lists.openwall.com" , Arnd Bergmann , X86 ML , "H. Peter Anvin" , Michael Ellerman Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1466 Lines: 33 On Tue, Nov 24, 2015 at 4:34 PM, Andy Lutomirski wrote: > On Nov 24, 2015 1:38 PM, "Kees Cook" wrote: >> >> One of the easiest ways to protect the kernel from attack is to reduce >> the internal attack surface exposed when a "write" flaw is available. By >> making as much of the kernel read-only as possible, we reduce the >> attack surface. >> >> Many things are written to only during __init, and never changed >> again. These cannot be made "const" since the compiler will do the wrong >> thing (we do actually need to write to them). Instead, move these items >> into a memory region that will be made read-only during mark_rodata_ro() >> which happens after all kernel __init code has finished. >> >> This introduces __read_only as a way to mark such memory, and adds some >> documentation about the existing __read_mostly marking. > > Obligatory bikeshed: __ro_after_init, please. It's barely longer, > and it directly explains what's going on. __read_only makes me think > that it's really read-only and could, for example, actually be in ROM. I'm fine with that. Anyone else want to chime in before I send a v2? -Kees -- Kees Cook Chrome OS & Brillo Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/