From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754193AbaI2LvE (ORCPT ); Mon, 29 Sep 2014 07:51:04 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59013 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753951AbaI2Lu1 (ORCPT ); Mon, 29 Sep 2014 07:50:27 -0400 Date: Mon, 29 Sep 2014 13:50:23 +0200 From: Jan Kara To: Yann Droneaud Cc: Heinrich Schuchardt , Andrew Morton , 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 Subject: Re: [PATCHv8.1] fanotify: enable close-on-exec on events' fd when requested in fanotify_init() Message-ID: <20140929115023.GB6328@quack.suse.cz> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1411980555-10818-1-git-send-email-ydroneaud@opteya.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 29-09-14 10:49:15, 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) > > Lookup also returned some wrong usage of the syscall: > > - in Gonk HAL from Mozilla Firefox OS sources[6]: > > mFd = fanotify_init(FAN_CLASS_NOTIF, FAN_CLOEXEC); > > Adding support for O_CLOEXEC in fanotify_init() won't magically > enable it for Gonk since FAN_CLOEXEC is defined as 0x1, which > is likely equal to O_WRONLY when used in open flag context. In > the other hand, it won't hurt it either. > > So this patch replaces call to macro get_unused_fd() by a call > to function get_unused_fd_flags() with event_f_flags value as > argument. This way O_CLOEXEC flag in the second argument of > fanotify_init(2) syscall is interpreted so that close-on-exec > get enabled when requested. > > [1] http://blog.ffwll.ch/2013/11/botching-up-ioctls.html > [2] http://cgit.freedesktop.org/systemd/systemd/tree/src/readahead/readahead-collect.c?id=v208#n294 > [3] https://github.com/xaionaro/clsync/blob/v0.2.1/sync.c#L1631 > https://github.com/xaionaro/clsync/blob/v0.2.1/configuration.h#L38 > [4] http://www.lanedo.com/~aleksander/fanotify/fanotify-example.c > [5] http://www.lanedo.com/2013/filesystem-monitoring-linux-kernel/ > [6] http://hg.mozilla.org/mozilla-central/file/325c74addeba/hal/gonk/GonkDiskSpaceWatcher.cpp#l167 > > Link: http://lkml.kernel.org/r/cover.1394532336.git.ydroneaud@opteya.com > Cc: Heinrich Schuchardt > Cc: Jan Kara > Cc: Valdis Kletnieks > Cc: Michael Kerrisk-manpages > Cc: Lino Sanfilippo > Cc: Richard Guy Briggs > Cc: Eric Paris > Cc: Al Viro > Cc: Andrew Morton > Cc: stable@vger.kernel.org > Cc: linux-api@vger.kernel.org > Reviewed by: Heinrich Schuchardt > Signed-off-by: Yann Droneaud The patch looks good. You can add: Reviewed-by: Jan Kara Honza > --- > Hi Andrew and Henrich, > > Please find an updated patch with a commit message fixed regarding > the obsolote comments on code which is now updated, thanks to > Heinrich's patch. > > Changes from v8: > - fixed commit message > - added Reviewed-by: > > Regards. > > Yann Droneaud, > OPTEYA > > fs/notify/fanotify/fanotify_user.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c > index b13992a41bd9..c991616acca9 100644 > --- a/fs/notify/fanotify/fanotify_user.c > +++ b/fs/notify/fanotify/fanotify_user.c > @@ -78,7 +78,7 @@ static int create_fd(struct fsnotify_group *group, > > pr_debug("%s: group=%p event=%p\n", __func__, group, event); > > - client_fd = get_unused_fd(); > + client_fd = get_unused_fd_flags(group->fanotify_data.f_flags); > if (client_fd < 0) > return client_fd; > > -- > 1.9.3 > -- Jan Kara SUSE Labs, CR