From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754391AbeDYOGE (ORCPT ); Wed, 25 Apr 2018 10:06:04 -0400 Received: from uhil19pa10.eemsg.mail.mil ([214.24.21.83]:2294 "EHLO uhil19pa10.eemsg.mail.mil" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753336AbeDYOGA (ORCPT ); Wed, 25 Apr 2018 10:06:00 -0400 X-IronPort-AV: E=Sophos;i="5.49,326,1520899200"; d="scan'208";a="11093547" IronPort-PHdr: =?us-ascii?q?9a23=3Aa4LYmRWvb2q2vSE5DQnHNe3A3E/V8LGtZVwlr6?= =?us-ascii?q?E/grcLSJyIuqrYZRaPvadThVPEFb/W9+hDw7KP9fy4AipYud6oizMrSNR0TR?= =?us-ascii?q?gLiMEbzUQLIfWuLgnFFsPsdDEwB89YVVVorDmROElRH9viNRWJ+iXhpTEdFQ?= =?us-ascii?q?/iOgVrO+/7BpDdj9it1+C15pbffxhEiCCybL9uIhi6txndutULioZ+N6g9zQ?= =?us-ascii?q?fErGFVcOpM32NoIlyTnxf45siu+ZNo7jpdtfE8+cNeSKv2Z6s3Q6BWAzQgKG?= =?us-ascii?q?A1+dbktQLfQguV53sTSXsZnxxVCAXY9h76X5Pxsizntuph3SSRIMP7QawoVT?= =?us-ascii?q?mk8qxmUwHjhjsZODEl8WHXks1wg7xdoBK9vBx03orYbJiIOPZiYq/ReNUXSm?= =?us-ascii?q?RbXsZVSidPHIWyYYUSBOYFJOpUsZXxq14IoBCjBwejGfnvxydViHHo06000+?= =?us-ascii?q?cvHw/I0wMvHd0BrHvaoc7pNKoQS+250LXEwDvBYv5QxDzz6JLIchckofyUQL?= =?us-ascii?q?xwbdTeyVEvFwzbiFWbtJHrPzaP2eQJt2iU8ephXv+ohm48tg5xuSOixtssi4?= =?us-ascii?q?bVhoIVzUrI9SNiwIkvP9G4R0l7YcC9HZZWqiqUNJN2T9s/T2xntys20L0LtY?= =?us-ascii?q?OhcCQUx5kr2QTTZ+GBfoOV+BzsTvyRLi19hH99fbK/gAu9/la4x+3nU8m0zE?= =?us-ascii?q?5Kri1YktnQrnwN1wLc6syASvZl4keuwyyP1wHO6uFfO0w0iaraJIIhwr43jJ?= =?us-ascii?q?YTt1jMHjTql0nsia+Wd0Ek9vCp6+ThfLrmuoeRO5J7hwzxKKgjmtGzDf4mPg?= =?us-ascii?q?UBQWSX4/mw2KXm/ULjQbVKivM2krPesJDfPckbvbO2AxRO34Y/6xewEzem0N?= =?us-ascii?q?MCkXkBN1JKYgiLj4fuO1HQOPz4F+uwg0ywkDd3wPDLJqDuApXKLnnNjrjheb?= =?us-ascii?q?J961VHxQop099Q+pJUBasdIP7pRkDxs9nYBAcjMwOo2+bnFMl91oQGVGKXGK?= =?us-ascii?q?CZLafSvESQ5u01PumMYJYZuDP6K/gi/f7hk2U1lkMafamsxZEXcmy3Hux6I0?= =?us-ascii?q?WFZnrhmtMBEWYMvgojQ+3mkVuCUTBIZ3upQaI86S80CJi8AYfAWI+tmrqB0z?= =?us-ascii?q?m/HpFMYWBGEF+MG2/yd4qYQ/cMdD6SIsh5nzwAVLihTZIh1B63uA/51bVnNO?= =?us-ascii?q?zU9TMctZ/4yth16PPclQso+Tx3EcudyWeNQH9wnm8SQD82xq9/q1Rnylifya?= =?us-ascii?q?h4n+BYFdtL6vNNUwc6M4PczuNjB9DpRA3OYsqJSEynQtW6ATA9V9cxw9gTbE?= =?us-ascii?q?ZgH9WtkAvO3zSlA7ALjbyHHp80/bzG33j3Ocl9z2zK1K47j1kpWsFPL3Gphr?= =?us-ascii?q?Zj9wjPAI7Ei1uZl6ewdaQbxyPM9XmMzWyPvEFGSgJwVaTFXXYCZkrZt9j54V?= =?us-ascii?q?nCT7C0BbQ6MQtL0dSCJbdSat31kVVGQ+/uONDfY2K3hmexCg+Exr2XbIX3ZW?= =?us-ascii?q?odwjvSCEwfngAN8naJKxI+Cj2io23AFjxuE0zgY0f2/el5snO7QVc+zxuWYE?= =?us-ascii?q?15y7q15hkViOSYS/MS2LIEpSggpyxuE1azxNLbEN6Apwt6fKVAetMx+lZH1W?= =?us-ascii?q?TXtwxnJJOvMr5tiUQDfAhtuEPuzRp3Wc18lp0GpW0rwEJSLr2V1FdaP2eU3Z?= =?us-ascii?q?fvN7nTMUHo8RyvYrKQ0VbbhoW44KAKvc8kpk3jsQfhLU8r93FqwpEByHeHzo?= =?us-ascii?q?nbBwoVF5TqWwA48AYs9OKSWTU0+46BjS4kCqKzqDKXnotzXOY=3D?= X-IPAS-Result: =?us-ascii?q?A2DEAgCSiuBa/wHyM5BbGgEBAQEBAgEBAQEIAQEBAYMYK?= =?us-ascii?q?4FbKINqlHlLBnopgQ+VBTYBhEACgwkhOBQBAgEBAQEBAQIBayiCNSQBgkkBB?= =?us-ascii?q?SNWEAsOCgICJgICVwYNBgIBAYJYgiYNpzCCHIRYg2yCP4EJhF6CKIEMgQeBM?= =?us-ascii?q?oI6LodzgjQgApgDCI4/BoE0hjqEYpFcMyGBUisIAhgIIQ+CfpBqIzB6AQGPK?= =?us-ascii?q?AEB?= Subject: Re: [PATCH 04/24] VFS: Add LSM hooks for filesystem context [ver #7] To: David Howells Cc: Paul Moore , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, viro@zeniv.linux.org.uk, selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org References: <152414466005.23902.12967974041384198114.stgit@warthog.procyon.org.uk> <152414469006.23902.8132059438921850399.stgit@warthog.procyon.org.uk> <3232.1524238511@warthog.procyon.org.uk> <703.1524583367@warthog.procyon.org.uk> From: Stephen Smalley Message-ID: <1bb08eac-517a-a07e-5e64-5771cc0c0afc@tycho.nsa.gov> Date: Wed, 25 Apr 2018 10:07:15 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <703.1524583367@warthog.procyon.org.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/24/2018 11:22 AM, David Howells wrote: > Stephen Smalley wrote: > >> Neither fsopen() nor fscontext_fs_write() appear to perform any kind of >> up-front permission checking (DAC or MAC), although some security hooks may >> be ultimately called to allocate structures, parse security options, etc. >> Is there a reason not apply a may_mount() or similar check up front? > > may_mount() is called by fsmount() at the moment. It may make sense to move > this earlier to fsopen(). Note that there's also going to be something that > looks like: > > fd = fspick("/mnt"); > fsmount(fd, "/a", MNT_NOEXEC); // ie. bind mount > > or: > > fd = fspick("/mnt"); > write(fd, "o intr"); > write(fd, "x reconfigure"); // ie. something like remount > close(fd); > > I guess we'd want to call may_mount() in fspick() too. But there's also the > possibility of using this to create a query interfact too: > > fd = fspick("/mnt"); > write(fd, "q intr"); > read(fd, value_buffer); My concern was that fsopen()/fscontext_fs_write() may expose attack surface (e.g. mount option parsing code) that might not be normally accessible to unprivileged userspace (i.e. gated by may_mount() and security_sb_mount()) prior to your changes.