From patchwork Sat May 16 02:08:27 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 6418741 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 6AE849F318 for ; Sat, 16 May 2015 02:13:22 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8456D20576 for ; Sat, 16 May 2015 02:13:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 707F020570 for ; Sat, 16 May 2015 02:13:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992691AbbEPCNS (ORCPT ); Fri, 15 May 2015 22:13:18 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:36279 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2992449AbbEPCNR (ORCPT ); Fri, 15 May 2015 22:13:17 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.2:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1YtRbI-00069S-TY; Fri, 15 May 2015 20:13:16 -0600 Received: from 67-3-205-90.omah.qwest.net ([67.3.205.90] helo=x220.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1YtRbH-0002Gw-UO; Fri, 15 May 2015 20:13:16 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Linux Containers Cc: , Linux API , "Serge E. Hallyn" , Andy Lutomirski , Richard Weinberger , Kenton Varda , Michael Kerrisk-manpages , =?utf-8?Q?St=C3=A9phane?= Graber , Eric Windisch , Greg Kroah-Hartman , Tejun Heo References: <87pp63jcca.fsf@x220.int.ebiederm.org> <87siaxuvik.fsf@x220.int.ebiederm.org> Date: Fri, 15 May 2015 21:08:27 -0500 In-Reply-To: <87siaxuvik.fsf@x220.int.ebiederm.org> (Eric W. Biederman's message of "Fri, 15 May 2015 21:05:39 -0500") Message-ID: <87y4kptgtg.fsf_-_@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 X-XM-AID: U2FsdGVkX1+g8Ja0QSKy3WyDFgCug6wvSOkAQXMzKqM= X-SA-Exim-Connect-IP: 67.3.205.90 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=2 X-Spam-Combo: ***;Linux Containers X-Spam-Relay-Country: X-Spam-Timing: total 400 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 3.8 (1.0%), b_tie_ro: 2.8 (0.7%), parse: 3.0 (0.7%), extract_message_metadata: 20 (4.9%), get_uri_detail_list: 3.5 (0.9%), tests_pri_-1000: 7 (1.8%), tests_pri_-950: 1.57 (0.4%), tests_pri_-900: 1.51 (0.4%), tests_pri_-400: 27 (6.8%), check_bayes: 26 (6.4%), b_tokenize: 9 (2.2%), b_tok_get_all: 8 (1.9%), b_comp_prob: 2.9 (0.7%), b_tok_touch_all: 3.3 (0.8%), b_finish: 0.85 (0.2%), tests_pri_0: 324 (81.0%), tests_pri_500: 7 (1.7%), rewrite_mail: 0.00 (0.0%) Subject: [CFT][PATCH 05/10] sysctl: Allow creating permanently empty directories that serve as mountpoints. X-SA-Exim-Version: 4.2.1 (built Wed, 24 Sep 2014 11:00:52 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add a magic sysctl table sysctl_mount_point that when used to create a directory forces that directory to be permanently empty. Update the code to use make_empty_dir_inode when accessing permanently empty directories. Update the code to not allow adding to permanently empty directories. Update /proc/sys/fs/binfmt_misc to be a permanently empty directory. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" --- fs/proc/proc_sysctl.c | 37 +++++++++++++++++++++++++++++++++++++ include/linux/sysctl.h | 3 +++ kernel/sysctl.c | 8 +------- 3 files changed, 41 insertions(+), 7 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index fea2561d773b..fdda62e6115e 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -19,6 +19,28 @@ static const struct inode_operations proc_sys_inode_operations; static const struct file_operations proc_sys_dir_file_operations; static const struct inode_operations proc_sys_dir_operations; +/* Support for permanently empty directories */ + +struct ctl_table sysctl_mount_point[] = { + { } +}; + +static bool is_empty_dir(struct ctl_table_header *head) +{ + return head->ctl_table[0].child == sysctl_mount_point; +} + +static void set_empty_dir(struct ctl_dir *dir) +{ + dir->header.ctl_table[0].child = sysctl_mount_point; +} + +static void clear_empty_dir(struct ctl_dir *dir) + +{ + dir->header.ctl_table[0].child = NULL; +} + void proc_sys_poll_notify(struct ctl_table_poll *poll) { if (!poll) @@ -187,6 +209,17 @@ static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header) struct ctl_table *entry; int err; + /* Is this a permanently empty directory? */ + if (is_empty_dir(&dir->header)) + return -EROFS; + + /* Am I creating a permanently empty directory? */ + if (header->ctl_table == sysctl_mount_point) { + if (!RB_EMPTY_ROOT(&dir->root)) + return -EINVAL; + set_empty_dir(dir); + } + dir->header.nreg++; header->parent = dir; err = insert_links(header); @@ -202,6 +235,8 @@ fail: erase_header(header); put_links(header); fail_links: + if (header->ctl_table == sysctl_mount_point) + clear_empty_dir(dir); header->parent = NULL; drop_sysctl_table(&dir->header); return err; @@ -419,6 +454,8 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, inode->i_mode |= S_IFDIR; inode->i_op = &proc_sys_dir_operations; inode->i_fop = &proc_sys_dir_file_operations; + if (is_empty_dir(head)) + make_empty_dir_inode(inode); } out: return inode; diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 795d5fea5697..fa7bc29925c9 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -188,6 +188,9 @@ struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path, void unregister_sysctl_table(struct ctl_table_header * table); extern int sysctl_init(void); + +extern struct ctl_table sysctl_mount_point[]; + #else /* CONFIG_SYSCTL */ static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table) { diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 2082b1a88fb9..c3eee4c6d6c1 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1531,12 +1531,6 @@ static struct ctl_table vm_table[] = { { } }; -#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE) -static struct ctl_table binfmt_misc_table[] = { - { } -}; -#endif - static struct ctl_table fs_table[] = { { .procname = "inode-nr", @@ -1690,7 +1684,7 @@ static struct ctl_table fs_table[] = { { .procname = "binfmt_misc", .mode = 0555, - .child = binfmt_misc_table, + .child = sysctl_mount_point, }, #endif {