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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 EE542C433E0 for ; Wed, 27 May 2020 22:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF92D2073B for ; Wed, 27 May 2020 22:38:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="QWaohhXI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726130AbgE0WiC (ORCPT ); Wed, 27 May 2020 18:38:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35972 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725385AbgE0WiC (ORCPT ); Wed, 27 May 2020 18:38:02 -0400 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25CA9C05BD1E for ; Wed, 27 May 2020 15:38:01 -0700 (PDT) Received: by mail-pf1-x443.google.com with SMTP id x13so12488147pfn.11 for ; Wed, 27 May 2020 15:38:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Eb+5CddLVa25XNVlonONbTANA1hlzWybPHX5/YlMRAg=; b=QWaohhXI7vTzQW1hXa2jmmmBa0brACBxQIsl8lefEyaqmYxDE3S3Ms+vdC0BFrlFrm /gypiaS3ie0c0fRgRR99iYuDdZASJ+XWkTao8u8e5i+tYCbH1KBcSZCRo445dsB6CWXL rnEvuUS94keZToK/N++qo7h0DwcqCCNGp/vA0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=Eb+5CddLVa25XNVlonONbTANA1hlzWybPHX5/YlMRAg=; b=DF5rAthpu1cIGENJ1v3oxz3UmOutaDCvWM6vB8HiU05FSXvK0dms3IO7rsajKiSXA9 Z6u4bozNpVq0sJA+aJ5fgnN22h4qxuZ8YFC9nV4q3oEF+r6oE4QbNLnczZIIMwvETprj T8aK+Uvo4F+5F+Wtv5TBoDel+rwvyzOytaMtRIwaJDZlCOzdj+rYgJdtmwyeUb/0RpYc a5gL8FVqqp8PlCydRzvk/YWX6pSyMDnj09ZtF9bIh/fQT4Sp6GPN7NxGwNS9ZrgOXllx bG9yORNolPU5jZ/XoSRkDNPjanWFbZoWpIB7/jm+ZilFJA9oz/1h+EkIweuUbgHkbVrg gYbA== X-Gm-Message-State: AOAM533C4ryn3npXZxKnqwx4YQdawxyuHuZxndm9bjXD+csZ3Zf5NNNo YB0yYlaeSFxbcRLURFQ1U019gQ== X-Google-Smtp-Source: ABdhPJwNlr3Xk8BEC7z5YcbAPjW8w6+3/+dYjwoTeOATU+UCkXCNrTGjHNY+VbH56DdDl559N6CXvg== X-Received: by 2002:a63:c5a:: with SMTP id 26mr10078pgm.270.1590619080709; Wed, 27 May 2020 15:38:00 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id u20sm3028646pfc.55.2020.05.27.15.37.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 May 2020 15:37:59 -0700 (PDT) Date: Wed, 27 May 2020 15:37:58 -0700 From: Kees Cook To: Christian Brauner Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Tycho Andersen , Matt Denton , Sargun Dhillon , Jann Horn , Chris Palmer , Aleksa Sarai , Robert Sesek , Jeffrey Vander Stoep , Linux Containers Subject: Re: [PATCH 1/2] seccomp: notify user trap about unused filter Message-ID: <202005271537.75548B6@keescook> References: <20200527111902.163213-1-christian.brauner@ubuntu.com> <202005271408.58F806514@keescook> <20200527220532.jplypougn3qzwrms@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200527220532.jplypougn3qzwrms@wittgenstein> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 28, 2020 at 12:05:32AM +0200, Christian Brauner wrote: > The main question also is, is there precedence where the kernel just > closes the file descriptor for userspace behind it's back? I'm not sure > I've heard of this before. That's not how that works afaict; it's also > not how we do pidfds. We don't just close the fd when the task > associated with it goes away, we notify and then userspace can close. But there's a mapping between pidfd and task struct that is separate from task struct itself, yes? I.e. keeping a pidfd open doesn't pin struct task in memory forever, right? -- Kees Cook