From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757210AbbA1ESX (ORCPT ); Tue, 27 Jan 2015 23:18:23 -0500 Received: from mail.kernel.org ([198.145.29.136]:38356 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756158AbbA1ESL (ORCPT ); Tue, 27 Jan 2015 23:18:11 -0500 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Yann Droneaud , "Mihai Don\\u021bu" , =?UTF-8?q?P=C3=A1draig=20Brady?= , Heinrich Schuchardt , Jan Kara , Valdis Kletnieks , Michael Kerrisk-manpages , Lino Sanfilippo , Richard Guy Briggs , Eric Paris , Al Viro , Andrew Morton , Linus Torvalds , Zefan Li Subject: [PATCH 3.4 049/177] fanotify: enable close-on-exec on events' fd when requested in fanotify_init() Date: Wed, 28 Jan 2015 12:07:45 +0800 Message-Id: <1422418236-12852-98-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1422418050-12581-1-git-send-email-lizf@kernel.org> References: <1422418050-12581-1-git-send-email-lizf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yann Droneaud 3.4.106-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 0b37e097a648aa71d4db1ad108001e95b69a2da4 upstream. 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)[1]. Unfortunately 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(). It's a pity, since, according to some lookup on various search engines and http://codesearch.debian.net/, there's already some userspace code which use O_CLOEXEC: - 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) Additionally, since commit 48149e9d3a7e ("fanotify: check file flags passed in fanotify_init"). having O_CLOEXEC as part of fanotify_init() second argument is expressly allowed. So it seems expected to set close-on-exec flag on the file descriptors if userspace is allowed to request it with O_CLOEXEC. But Andrew Morton raised[6] the concern that enabling now close-on-exec might break existing applications which ask for O_CLOEXEC but expect the file descriptor to be inherited across exec(). In the other hand, as reported by Mihai Dontu[7] close-on-exec on the file descriptor returned as part of file access notify can break applications due to deadlock. So close-on-exec is needed for most applications. More, applications asking for close-on-exec are likely expecting it to be enabled, relying on O_CLOEXEC being effective. If not, it might weaken their security, as noted by Jan Kara[8]. 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 and close-on-exec get enabled when requested. [1] http://man7.org/linux/man-pages/man2/fanotify_init.2.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://lkml.kernel.org/r/20141001153621.65e9258e65a6167bf2e4cb50@linux-foundation.org [7] http://lkml.kernel.org/r/20141002095046.3715eb69@mdontu-l [8] http://lkml.kernel.org/r/20141002104410.GB19748@quack.suse.cz Link: http://lkml.kernel.org/r/cover.1411562410.git.ydroneaud@opteya.com Signed-off-by: Yann Droneaud Reviewed-by: Jan Kara Reviewed by: Heinrich Schuchardt Tested-by: Heinrich Schuchardt Cc: Mihai Don\u021bu Cc: Pádraig Brady 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: Michael Kerrisk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Zefan Li --- 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 48bc91d..97d91f0 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -67,7 +67,7 @@ static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event) 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; -- 1.9.1