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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2995DC43334 for ; Mon, 13 Jun 2022 21:55:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 885378D01E4; Mon, 13 Jun 2022 17:55:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 830B46B0259; Mon, 13 Jun 2022 17:55:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D1A88D01E4; Mon, 13 Jun 2022 17:55:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 5BAC26B0258 for ; Mon, 13 Jun 2022 17:55:44 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 37A0280EF0 for ; Mon, 13 Jun 2022 21:55:44 +0000 (UTC) X-FDA: 79574570208.29.CF950CE Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf08.hostedemail.com (Postfix) with ESMTP id 472F5160095 for ; Mon, 13 Jun 2022 21:55:43 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5F16661468; Mon, 13 Jun 2022 21:55:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3BCAC34114; Mon, 13 Jun 2022 21:55:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1655157341; bh=AF0PJZhUcs0mBF42nPc3xhzkjbqEMjUTmXKOM9WAw0w=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gp1jX8WfBHjFifwdWq/r3rM+5ff1PyLfsrvNPCjL/KEoA5z0WY0FtNdKvktKG0/H1 OB+hODIpwiz5HZLXvMhRq56RlFjgs5LTz+/hue49mnCAYI6yqm1CSfpP6KU4dZUWQ/ m3cc6+SIkl7LrNXdoQsOBT4vqiuz9nkbOs5BVJN8= Date: Mon, 13 Jun 2022 14:55:40 -0700 From: Andrew Morton To: Axel Rasmussen Cc: Alexander Viro , Charan Teja Reddy , Dave Hansen , "Dmitry V . Levin" , Gleb Fotengauer-Malinovskiy , Hugh Dickins , Jan Kara , Jonathan Corbet , Mel Gorman , Mike Kravetz , Mike Rapoport , Nadav Amit , Peter Xu , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , zhangyi , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 2/6] userfaultfd: add /dev/userfaultfd for fine grained access control Message-Id: <20220613145540.1c9f7750092911bae1332b92@linux-foundation.org> In-Reply-To: <20220601210951.3916598-3-axelrasmussen@google.com> References: <20220601210951.3916598-1-axelrasmussen@google.com> <20220601210951.3916598-3-axelrasmussen@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=gp1jX8Wf; dmarc=none; spf=pass (imf08.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655157343; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=thr8FTW5Ym/DZ+iY5UnyQF5IDmU6t6HdQjlSfTLC/2c=; b=qjrD3guG9u7aWqFr16z8JaZPZOJVtI82xzsCZ0KNuOb57v1vGUPIoRa92qZ6rnw58oCPek Jgu06+tZLc0KL4CybPGB9ioQlaadYtbEpIsl5cBxZsW/KCsT4LIcO4qFHqMs6Ft7tce1uN jzytPy2vCsXjkfA73tnVSBcqrZ1gnis= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655157343; a=rsa-sha256; cv=none; b=1dB+lsm9LWnTuLfQPll28B05g5yIa5yMw1K95pXLqZhfzlDV/3k8+JHgKMtjXdUZOPOMH7 o3c9BMwxaJBayW+ICKc+fRS4mtJRYTSmkAfUqhqUzT/GIrpf4B81x2FyW/mtzRbqOluCgY siSD8xUJOQvVT+FcGK0i32Koa5YlEP0= X-Stat-Signature: 4ysif8y8ozwdfpfn9cgkj9zr1tsdmg8f X-Rspamd-Queue-Id: 472F5160095 X-Rspam-User: Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=gp1jX8Wf; dmarc=none; spf=pass (imf08.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam10 X-HE-Tag: 1655157343-690336 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 1 Jun 2022 14:09:47 -0700 Axel Rasmussen wrote: > To achieve this, add a /dev/userfaultfd misc device. This device > provides an alternative to the userfaultfd(2) syscall for the creation > of new userfaultfds. The idea is, any userfaultfds created this way will > be able to handle kernel faults, without the caller having any special > capabilities. Access to this mechanism is instead restricted using e.g. > standard filesystem permissions. The use of a /dev node isn't pretty. Why can't this be done by tweaking sys_userfaultfd() or by adding a sys_userfaultfd2()? Peter, will you be completing review of this patchset?