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=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 2E945C32792 for ; Thu, 3 Oct 2019 19:39:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0ADD920862 for ; Thu, 3 Oct 2019 19:39:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732861AbfJCTjd (ORCPT ); Thu, 3 Oct 2019 15:39:33 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56499 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731412AbfJCTjc (ORCPT ); Thu, 3 Oct 2019 15:39:32 -0400 Received: from [213.220.153.21] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1iG6wj-0003Qd-67; Thu, 03 Oct 2019 19:39:29 +0000 Date: Thu, 3 Oct 2019 21:39:28 +0200 From: Christian Brauner To: Dmitry Vyukov Cc: Marco Elver , Joel Fernandes , kasan-dev , LKML , Andrey Konovalov , Alexander Potapenko , "Paul E. McKenney" , Paul Turner , Daniel Axtens , Anatol Pomazau , Will Deacon , Andrea Parri , Alan Stern , LKMM Maintainers -- Akira Yokosawa , Nicholas Piggin , Boqun Feng , Daniel Lustig , Jade Alglave , Luc Maranget Subject: Re: Kernel Concurrency Sanitizer (KCSAN) Message-ID: <20191003193927.fvkc4tu66guv7edu@wittgenstein> References: <20191001211948.GA42035@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 03, 2019 at 06:00:38PM +0200, Dmitry Vyukov wrote: > On Thu, Oct 3, 2019 at 3:13 PM Dmitry Vyukov wrote: > > > > On Wed, Oct 2, 2019 at 9:52 PM Marco Elver wrote: > > > > > > Hi Joel, > > > > > > On Tue, 1 Oct 2019 at 23:19, Joel Fernandes wrote: > > > > > > > > On Fri, Sep 20, 2019 at 04:18:57PM +0200, Marco Elver wrote: > > > > > Hi all, > > > > > > > > > > We would like to share a new data-race detector for the Linux kernel: > > > > > Kernel Concurrency Sanitizer (KCSAN) -- > > > > > https://github.com/google/ktsan/wiki/KCSAN (Details: > > > > > https://github.com/google/ktsan/blob/kcsan/Documentation/dev-tools/kcsan.rst) > > > > > > > > > > To those of you who we mentioned at LPC that we're working on a > > > > > watchpoint-based KTSAN inspired by DataCollider [1], this is it (we > > > > > renamed it to KCSAN to avoid confusion with KTSAN). > > > > > [1] http://usenix.org/legacy/events/osdi10/tech/full_papers/Erickson.pdf > > > > > > > > > > In the coming weeks we're planning to: > > > > > * Set up a syzkaller instance. > > > > > * Share the dashboard so that you can see the races that are found. > > > > > * Attempt to send fixes for some races upstream (if you find that the > > > > > kcsan-with-fixes branch contains an important fix, please feel free to > > > > > point it out and we'll prioritize that). > > > > > > > > > > There are a few open questions: > > > > > * The big one: most of the reported races are due to unmarked > > > > > accesses; prioritization or pruning of races to focus initial efforts > > > > > to fix races might be required. Comments on how best to proceed are > > > > > welcome. We're aware that these are issues that have recently received > > > > > attention in the context of the LKMM > > > > > (https://lwn.net/Articles/793253/). > > > > > * How/when to upstream KCSAN? > > > > > > > > Looks exciting. I think based on our discussion at LPC, you mentioned > > > > one way of pruning is if the compiler generated different code with _ONCE > > > > annotations than what would have otherwise been generated. Is that still on > > > > the table, for the purposing of pruning the reports? > > > > > > This might be interesting at first, but it's not entirely clear how > > > feasible it is. It's also dangerous, because the real issue would be > > > ignored. It may be that one compiler version on a particular > > > architecture generates the same code, but any change in compiler or > > > architecture and this would no longer be true. Let me know if you have > > > any more ideas. > > > > > > Best, > > > -- Marco > > > > > > > Also appreciate a CC on future patches as well. > > > > > > > > thanks, > > > > > > > > - Joel > > > > > > > > > > > > > > > > > > Feel free to test and send feedback. > > > > FYI https://twitter.com/grsecurity/status/1179736828880048128 :) > > +Christian opts in for _all_ reports for > kernel/{fork,exit,pid,signal}.c and friends. > Just wanted it to be written down for future reference :) Yes, please! :) Christian