From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751475AbaJBGVH (ORCPT ); Thu, 2 Oct 2014 02:21:07 -0400 Received: from ou.quest-ce.net ([195.154.187.82]:60648 "EHLO ou.quest-ce.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751185AbaJBGVF (ORCPT ); Thu, 2 Oct 2014 02:21:05 -0400 Message-ID: <1412230855.28184.5.camel@localhost.localdomain> From: Yann Droneaud To: Andrew Morton Cc: Heinrich Schuchardt , Eric Paris , Richard Guy Briggs , Al Viro , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org, linux-api@vger.kernel.org, Jan Kara , Lino Sanfilippo , Valdis Kletnieks , Michael Kerrisk-manpages , Yann Droneaud Date: Thu, 02 Oct 2014 08:20:55 +0200 In-Reply-To: <20141001153621.65e9258e65a6167bf2e4cb50@linux-foundation.org> References: <9d050a2db4f9cf68cd6cb038f16cccb0f73c6e66.1411562410.git.ydroneaud@opteya.com> <542481B3.8070300@gmx.de> <1411721898.7778.18.camel@localhost.localdomain> <542666B2.9080700@gmx.de> <1411980555-10818-1-git-send-email-ydroneaud@opteya.com> <20141001153621.65e9258e65a6167bf2e4cb50@linux-foundation.org> Organization: OPTEYA Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4 (3.10.4-4.fc20) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2a01:e35:2e9f:6ac0:1d34:d55:2d28:af2e X-SA-Exim-Mail-From: ydroneaud@opteya.com Subject: Re: [PATCHv8.1] fanotify: enable close-on-exec on events' fd when requested in fanotify_init() X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on ou.quest-ce.net) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Le mercredi 01 octobre 2014 à 15:36 -0700, Andrew Morton a écrit : > On Mon, 29 Sep 2014 10:49:15 +0200 Yann Droneaud wrote: > > > According to commit 80af258867648 ('fanotify: groups can specify > > their f_flags for new fd'), file descriptors created as part of > > file access notification events inherit flags from the > > event_f_flags argument passed to syscall fanotify_init(2). > > > > So while it is legal for userspace to call fanotify_init() with > > O_CLOEXEC as part of its second argument, O_CLOEXEC is currently > > silently ignored. > > > > Indeed event_f_flags are only given to dentry_open(), which only > > seems to care about O_ACCMODE and O_PATH in do_dentry_open(), > > O_DIRECT in open_check_o_direct() and O_LARGEFILE in > > generic_file_open(). > > > > But it seems logical to set close-on-exec flag on the file > > descriptor if userspace is allowed to request it with O_CLOEXEC. > > > > In fact, according to some lookup on http://codesearch.debian.net/ > > and various search engine, there's already some userspace code > > requesting it: > > > > - in systemd's readahead[2]: > > > > fanotify_fd = fanotify_init(FAN_CLOEXEC|FAN_NONBLOCK, O_RDONLY|O_LARGEFILE|O_CLOEXEC|O_NOATIME); > > > > - in clsync[3]: > > > > #define FANOTIFY_EVFLAGS (O_LARGEFILE|O_RDONLY|O_CLOEXEC) > > > > int fanotify_d = fanotify_init(FANOTIFY_FLAGS, FANOTIFY_EVFLAGS); > > > > - in examples [4] from "Filesystem monitoring in the Linux > > kernel" article[5] by Aleksander Morgado: > > > > if ((fanotify_fd = fanotify_init (FAN_CLOEXEC, > > O_RDONLY | O_CLOEXEC | O_LARGEFILE)) < 0) > > So we have a number of apps which are setting O_CLOEXEC, but it doesn't > actually work. With this change it *will* work, so the behaviour of > those apps might change, possibly breaking them? > In the other hand, not enabling close-on-exec might expose unwanted file descriptor to childs, creating security issues. YMMV. -- Yann Droneaud OPTEYA