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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 E8A37C64EBC for ; Thu, 4 Oct 2018 07:45:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A99AA21470 for ; Thu, 4 Oct 2018 07:45:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A99AA21470 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727654AbeJDOgz (ORCPT ); Thu, 4 Oct 2018 10:36:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:38526 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727589AbeJDOgz (ORCPT ); Thu, 4 Oct 2018 10:36:55 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7A174AC36; Thu, 4 Oct 2018 07:44:58 +0000 (UTC) Date: Thu, 4 Oct 2018 09:44:57 +0200 From: Michal Hocko To: Dan Williams Cc: akpm@linux-foundation.org, Dave Hansen , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/3] Randomize free memory Message-ID: <20181004074457.GD22173@dhcp22.suse.cz> References: <153861931865.2863953.11185006931458762795.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <153861931865.2863953.11185006931458762795.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 03-10-18 19:15:18, Dan Williams wrote: > Changes since v1: > * Add support for shuffling hot-added memory (Andrew) > * Update cover letter and commit message to clarify the performance impact > and relevance to future platforms I believe this hasn't addressed my questions in http://lkml.kernel.org/r/20181002143015.GX18290@dhcp22.suse.cz. Namely " It is the more general idea that I am not really sure about. First of all. Does it make _any_ sense to randomize 4MB blocks by default? Why cannot we simply have it disabled? Then and more concerning question is, does it even make sense to have this randomization applied to higher orders than 0? Attacker might fragment the memory and keep recycling the lowest order and get the predictable behavior that we have right now. " > [1]: https://lkml.org/lkml/2018/9/15/366 -- Michal Hocko SUSE Labs