From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7F20C433DF for ; Thu, 21 May 2020 23:43:44 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 01A4B207D8 for ; Thu, 21 May 2020 23:43:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01A4B207D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18855-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 12235 invoked by uid 550); 21 May 2020 23:43:37 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 12215 invoked from network); 21 May 2020 23:43:37 -0000 From: Thomas Gleixner To: Kees Cook Cc: Kristen Carlson Accardi , mingo@redhat.com, bp@alien8.de, arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com Subject: Re: [PATCH v2 0/9] Function Granular KASLR In-Reply-To: <202005211604.86AE1C2@keescook> Date: Fri, 22 May 2020 01:43:15 +0200 Message-ID: <87tv08svl8.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Kees, Kees Cook writes: > On Fri, May 22, 2020 at 12:26:30AM +0200, Thomas Gleixner wrote: >> I understand how this is supposed to work, but I fail to find an >> explanation how all of this is preserving the text subsections we have, >> i.e. .kprobes.text, .entry.text ...? > > I had the same question when I first started looking at earlier versions > of this series! :) > >> I assume that the functions in these subsections are reshuffled within >> their own randomized address space so that __xxx_text_start and >> __xxx_text_end markers still make sense, right? > > No, but perhaps in the future. Right now, they are entirely ignored and > left untouched. I'm fine with that restriction, but for a moment I got worried that this might screw up explicit subsections. This really want's to be clearly expressed in the cover letter and the changelogs so that such questions don't arise again. > So, before any of that, just .text.* is a good first step, and after > that I think next would be getting .text randomized relative to the other > .text.* sections (IIUC, it is entirely untouched currently, so only the > standard KASLR base offset moves it around). Only after that do we start > poking around trying to munge the special section contents (which > requires use solving a few problems simultaneously). :) Thanks for the detailed explanation! tglx