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 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 32F6DC5DF63 for ; Wed, 6 Nov 2019 14:16:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0326920869 for ; Wed, 6 Nov 2019 14:16:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731920AbfKFOQc (ORCPT ); Wed, 6 Nov 2019 09:16:32 -0500 Received: from l2mail1.panix.com ([166.84.1.75]:50702 "EHLO l2mail1.panix.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727478AbfKFOQb (ORCPT ); Wed, 6 Nov 2019 09:16:31 -0500 X-Greylist: delayed 926 seconds by postgrey-1.27 at vger.kernel.org; Wed, 06 Nov 2019 09:16:30 EST Received: from mailbackend.panix.com (mailbackend.panix.com [166.84.1.89]) by l2mail1.panix.com (Postfix) with ESMTPS id 477Sqj3NDGzFGw; Wed, 6 Nov 2019 09:01:05 -0500 (EST) Received: from mail-io1-f51.google.com (mail-io1-f51.google.com [209.85.166.51]) by mailbackend.panix.com (Postfix) with ESMTPSA id 477Sqh2bHWz14BZ; Wed, 6 Nov 2019 09:01:04 -0500 (EST) Received: by mail-io1-f51.google.com with SMTP id k1so15264588ioj.6; Wed, 06 Nov 2019 06:01:03 -0800 (PST) X-Gm-Message-State: APjAAAW30bdjrwoPxeQ+iEMF8z1CV67HC3DFxqmDKz/ZNvREcNfUWjOF nRA2UU0sLTo0hTmRxJ/RDCtYUe0MXyqs+ilgIds= X-Google-Smtp-Source: APXvYqyNiiZ980P2aQYdN2JGZ2ay2hIizWuWJTEwXvcdX3q2z/Mm48i+X6g4IkKCzWPTnAKbEi9ZHkCaXH06gLiiYmk= X-Received: by 2002:a5d:9ecd:: with SMTP id a13mr20356555ioe.270.1573048863570; Wed, 06 Nov 2019 06:01:03 -0800 (PST) MIME-Version: 1.0 References: <20191104002909.25783-1-shawn@git.icu> <87woceslfs.fsf@oldenburg2.str.redhat.com> <87sgn2skm6.fsf@oldenburg2.str.redhat.com> In-Reply-To: From: Zack Weinberg Date: Wed, 6 Nov 2019 09:00:51 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC v2 PATCH] futex: extend set_robust_list to allow 2 locking ABIs at the same time. To: Thomas Gleixner Cc: "Carlos O'Donell" , Florian Weimer , Shawn Landden , GNU C Library , linux-api@vger.kernel.org, LKML , Arnd Bergmann , Deepa Dinamani , Oleg Nesterov , Andrew Morton , Catalin Marinas , Keith Packard , Peter Zijlstra Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 5, 2019 at 9:28 AM Thomas Gleixner wrote: > > The real issue is that the robust list could be circular by incident or > malice and there is no way for the kernel to figure that out. That would > prevent the task from exiting and make it iterate over the list until > doomsday, i.e. a nice unpriviledged DoS. Why can't the kernel use the standard tortoise-and-hare algorithm for detecting circular linked lists here? zw