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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS autolearn=unavailable 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 A5383C43381 for ; Fri, 15 Mar 2019 16:15:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 75A6921871 for ; Fri, 15 Mar 2019 16:15:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="hKHmU445" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729465AbfCOQPh (ORCPT ); Fri, 15 Mar 2019 12:15:37 -0400 Received: from mail-vk1-f194.google.com ([209.85.221.194]:42663 "EHLO mail-vk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729455AbfCOQPh (ORCPT ); Fri, 15 Mar 2019 12:15:37 -0400 Received: by mail-vk1-f194.google.com with SMTP id j195so2320518vkj.9 for ; Fri, 15 Mar 2019 09:15:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kE5A+CZCQ970cuz5dKKKfTnoUsaz55mW0Rz8hAw/vKE=; b=hKHmU445IW/COhLh4C9icWVxuotJ3n1hCtm7Gll2wbtPW4oq5SvQlNfsGLiOslggPx rRw566RrEYUaSv3edGRRW9MQlE5W4+P4BUQWyE/f7O72f0uo/ZBhU4H5d4B68siXDRbD lEjpw9QGwmZcXVVIIqjXAyY0txLfCl7Z36WBI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=kE5A+CZCQ970cuz5dKKKfTnoUsaz55mW0Rz8hAw/vKE=; b=VEy2owoZ8zn+Hex0HNJ2X5jL1njuWR5KJbN451Ljuh+SbsFvw2D80XVIYEnB/8nNRH 5lJMpAtCvSI8lx6S77yI9qeqNTb/OBoydHduV9rHB/UhnsxygUYiwworyp8vIuUuTOYu SYlGFLoV9dO2QK+xKzbAAQiaQUWjLPLEVEhbf8SkBeLGmJKOStuKSak9ZZblSuvNfyOE rQVfkWdv/ZDwTWPbcwAjyJ9BLB0qO1Re/G1JYhyFl3h6Bc/yeM1yT8CrI8pSnJThElUd ABDnGn40X8m5FyDsMtGRp/S2Co4J6AIO17OzGNMxealiHau8eYAi38AlXYwLDGAxaJ7o DZrQ== X-Gm-Message-State: APjAAAV1qQQC8UqYPGPBfsuUAUn9HJ5hyJDXQ6E1mz8admwI/c9FoFFt sCsr0cQme5LsSEugosJFaDajknV8NP4= X-Google-Smtp-Source: APXvYqzW51hwELkw82F4qeW/TbGbWDs3d9ceL7vHLzVjL1fM0bBd7JA9XlnfJiLPBAk/L3OQ5Bmo0A== X-Received: by 2002:a1f:8bcd:: with SMTP id n196mr2445060vkd.33.1552666535434; Fri, 15 Mar 2019 09:15:35 -0700 (PDT) Received: from mail-vs1-f44.google.com (mail-vs1-f44.google.com. [209.85.217.44]) by smtp.gmail.com with ESMTPSA id g17sm40114uah.7.2019.03.15.09.15.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Mar 2019 09:15:35 -0700 (PDT) Received: by mail-vs1-f44.google.com with SMTP id c189so5702775vsd.9 for ; Fri, 15 Mar 2019 09:15:34 -0700 (PDT) X-Received: by 2002:a67:fa45:: with SMTP id j5mr2431791vsq.48.1552666196638; Fri, 15 Mar 2019 09:09:56 -0700 (PDT) MIME-Version: 1.0 References: <20190311093701.15734-1-peterx@redhat.com> <58e63635-fc1b-cb53-a4d1-237e6b8b7236@oracle.com> <20190313060023.GD2433@xz-x1> <3714d120-64e3-702e-6eef-4ef253bdb66d@redhat.com> <20190313185230.GH25147@redhat.com> <1934896481.7779933.1552504348591.JavaMail.zimbra@redhat.com> <20190313234458.GJ25147@redhat.com> <298b9469-abd2-b02b-5c71-529b8976a46c@redhat.com> <20190314161630.GS25147@redhat.com> In-Reply-To: <20190314161630.GS25147@redhat.com> From: Kees Cook Date: Fri, 15 Mar 2019 09:09:45 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 0/3] userfaultfd: allow to forbid unprivileged users To: Andrea Arcangeli Cc: Paolo Bonzini , Peter Xu , Mike Kravetz , LKML , Hugh Dickins , Luis Chamberlain , Maxime Coquelin , KVM , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Denis Plotnikov , Linux-MM , Marty McFadden , Maya Gokhale , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "linux-fsdevel@vger.kernel.org" , "Dr . David Alan Gilbert" , Andrew Morton Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Mar 14, 2019 at 9:16 AM Andrea Arcangeli wrote: > So this will be for who's paranoid and prefers to disable userfaultfd > as a whole as an hardening feature like the bpf sysctl allows: it will > allow to block uffd syscall without having to rebuild the kernel with > CONFIG_USERFAULTFD=n in environments where seccomp cannot be easily > enabled (i.e. without requiring userland changes). > > That's very fine with me, but then it wasn't me complaining in the > first place. Kees? I'm fine with a boolean. I just wanted to find a way to disable at runtime (so distro users had it available to them). -- Kees Cook