From patchwork Fri Mar 31 15:25:11 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kirill Tkhai X-Patchwork-Id: 9656625 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 73812601D2 for ; Fri, 31 Mar 2017 15:25:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 661AD28616 for ; Fri, 31 Mar 2017 15:25:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5AC52286CB; Fri, 31 Mar 2017 15:25:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E3F5828616 for ; Fri, 31 Mar 2017 15:25:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933382AbdCaPZ1 (ORCPT ); Fri, 31 Mar 2017 11:25:27 -0400 Received: from mail-eopbgr40122.outbound.protection.outlook.com ([40.107.4.122]:17312 "EHLO EUR03-DB5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933140AbdCaPZZ (ORCPT ); Fri, 31 Mar 2017 11:25:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=virtuozzo.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=ZAXQPqsscJGGP8/pMoWeZgn2Q69nd4f+PBpavt7Kx4Y=; b=hzrJzZfnzXrR20xKRdCWHKdLGBtJD2u3JUIHKoC29NS5We5wIPDEYkRKq6c6ofHmgy2Rp3huyR3pN2mrDd+70ghfP3/fPWLlhtQWn4n6KQZboNL8Z7A2h0Et0DCjE8yj76kQwrXEh4/CrfI4w5vW6UoWRnMc1FPGovRtU9y8xmg= Authentication-Results: hallyn.com; dkim=none (message not signed) header.d=none; hallyn.com; dmarc=none action=none header.from=virtuozzo.com; Received: from [172.16.25.3] (195.214.232.6) by HE1PR0802MB2283.eurprd08.prod.outlook.com (10.172.127.13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.991.14; Fri, 31 Mar 2017 15:25:17 +0000 Subject: Re: [PATCH RESEND 2/2] pidns: Expose task pid_ns_for_children to userspace To: Kees Cook , Michael Kerrisk References: <149086931397.4388.9604947335273204415.stgit@localhost.localdomain> <149086967937.4388.471494976517194744.stgit@localhost.localdomain> <20170330150520.1bdf20e599ff464bda0776b9@linux-foundation.org> <20170331010409.GA22895@outlook.office365.com> <0825f166-6f20-59a9-45a9-5ffe9009150e@virtuozzo.com> CC: Andrei Vagin , Andrew Morton , Andreas Gruenbacher , Linux API , LKML , Al Viro , Oleg Nesterov , Paul Moore , "Eric W. Biederman" , Andrew Vagin , "linux-fsdevel@vger.kernel.org" , Andy Lutomirski , Ingo Molnar , "Serge E. 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20:KcsXH9REWYxz28znpTlym0xgMaTbm/DiUuh1Ie9SL2Y7Ys1UFEDYI1Oj6ZwWFmD0vpfvcdISg9B4zARKUypSkQ0WhbEuZfcFyBReSFJSvqIC5Ukpuo3yi2IlLq0t+Q6jH0pbSmEHDjfEVqUlHwqBgBU4OrUDKKjjc0o5f6iY/1w= X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Mar 2017 15:25:17.6089 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0802MB2283 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 On 31.03.2017 18:06, Kees Cook wrote: > On Fri, Mar 31, 2017 at 2:45 AM, Kirill Tkhai wrote: >> On 31.03.2017 04:04, Andrei Vagin wrote: >>> On Thu, Mar 30, 2017 at 03:05:20PM -0700, Andrew Morton wrote: >>>> On Thu, 30 Mar 2017 13:27:59 +0300 Kirill Tkhai wrote: >>>> >>>>> pid_ns_for_children set by a task is known only to the task itself, >>>>> and it's impossible to identify it from outside. >>>>> >>>>> It's a big problem for checkpoint/restore software like CRIU, >>>>> because it can't correctly handle tasks, that do setns(CLONE_NEWPID) >>>>> in proccess of their work. >>>>> >>>>> This patch solves the problem, and it exposes pid_ns_for_children >>>>> to ns directory in standard way with the name "pid_for_children": >>>>> >>>>> ~# ls /proc/5531/ns -l | grep pid >>>>> lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] >>>>> lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] >>>>> >>>>> --- a/fs/proc/namespaces.c >>>>> +++ b/fs/proc/namespaces.c >>>>> @@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { >>>>> #endif >>>>> #ifdef CONFIG_PID_NS >>>>> &pidns_operations, >>>>> + &pidns_for_children_operations, >>>>> #endif >>>> >>>> This interface should be documented somewhere under Documentation/. >>>> But I can't immediately find where the /proc/pid/ns/ pseudo-files are >>>> documented... >>> >>> I know that they are documented in man7/namespaces.7 >>> >>> https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man7/namespaces.7#n187 >> >> I suggest the below patch, but it's too early for the man description till >> the feature is in mainline, because the man page requires commit id of the feature. >> >> [PATCH] namespaces.7: Document the /proc/[pid]/ns/pid_for_children file >> >> Signed-off-by: Kirill Tkhai >> --- >> man7/namespaces.7 | 10 +++++++++- >> 1 file changed, 9 insertions(+), 1 deletion(-) >> diff --git a/man7/namespaces.7 b/man7/namespaces.7 >> index 6dfceaa2a..06041774f 100644 >> --- a/man7/namespaces.7 >> +++ b/man7/namespaces.7 >> @@ -125,6 +125,7 @@ lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 ipc \-> ipc:[4026531839] >> lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 mnt \-> mnt:[4026531840] >> lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 net \-> net:[4026531969] >> lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid \-> pid:[4026531836] >> +lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid_for_children -> pid:[4026531834] > > Minor nit: this needs to be "\-" for the "-" Thanks, Kees. The updated version is below: [PATCH] namespaces.7: Document the /proc/[pid]/ns/pid_for_children file Signed-off-by: Kirill Tkhai --- man7/namespaces.7 | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/man7/namespaces.7 b/man7/namespaces.7 index 6dfceaa2a..b4e9b13f0 100644 --- a/man7/namespaces.7 +++ b/man7/namespaces.7 @@ -125,6 +125,7 @@ lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 ipc \-> ipc:[4026531839] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 mnt \-> mnt:[4026531840] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 net \-> net:[4026531969] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid \-> pid:[4026531836] +lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 pid_for_children \-> pid:[4026531834] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 user \-> user:[4026531837] lrwxrwxrwx. 1 mtk mtk 0 Apr 28 12:46 uts \-> uts:[4026531838] .fi @@ -186,7 +187,14 @@ This file is a handle for the network namespace of the process. .TP .IR /proc/[pid]/ns/pid " (since Linux 3.8)" .\" commit 57e8391d327609cbf12d843259c968b9e5c1838f -This file is a handle for the PID namespace of the process. +This file is a handle for the PID namespace of the process. It's +permanent during the whole process life. +.TP +.IR /proc/[pid]/ns/pid_for_children " (since Linux 4.12)" +.\" commit FIXME +This file is a handle for the PID namespace of a next born child +of the process. It's changed after unshare(2) and via setns(2), +so the file may differ from /proc/[pid]/ns/pid. .TP .IR /proc/[pid]/ns/user " (since Linux 3.8)" .\" commit cde1975bc242f3e1072bde623ef378e547b73f91