From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56B3CC433FF for ; Mon, 12 Aug 2019 16:37:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F65720679 for ; Mon, 12 Aug 2019 16:37:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726944AbfHLQhP (ORCPT ); Mon, 12 Aug 2019 12:37:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725843AbfHLQhO (ORCPT ); Mon, 12 Aug 2019 12:37:14 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1D6763D956; Mon, 12 Aug 2019 16:37:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id EB56F5C1B5; Mon, 12 Aug 2019 16:37:11 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 12 Aug 2019 18:37:13 +0200 (CEST) Date: Mon, 12 Aug 2019 18:37:10 +0200 From: Oleg Nesterov To: Adrian Reber Cc: Christian Brauner , Eric Biederman , Pavel Emelianov , Jann Horn , Dmitry Safonov <0x7f454c46@gmail.com>, linux-kernel@vger.kernel.org, Andrei Vagin , Mike Rapoport , Radostin Stoyanov Subject: Re: [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Message-ID: <20190812163710.GC31560@redhat.com> References: <20190811203327.5385-1-areber@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190811203327.5385-1-areber@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 12 Aug 2019 16:37:14 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/11, Adrian Reber wrote: > > include/linux/pid.h | 2 +- > include/linux/sched/task.h | 1 + > include/uapi/linux/sched.h | 1 + > kernel/fork.c | 22 ++++++++++++++++++++-- > kernel/pid.c | 36 +++++++++++++++++++++++++++++------- > 5 files changed, 52 insertions(+), 10 deletions(-) Looks good to me... A couple of nits below, but I won't insist, feel free to ignore. > +/* > + * Different sizes of struct clone_args > + */ > +#define CLONE3_ARGS_SIZE_V0 64 I don't really understand why do we want the "size < CLONE3_ARGS_SIZE_V0" check in copy_clone_args_from_user(), but I won't argue. > +/* V1 includes set_tid */ > +#define CLONE3_ARGS_SIZE_V1 72 unused? > @@ -2031,7 +2038,13 @@ static __latent_entropy struct task_struct *copy_process( > stackleak_task_init(p); > > if (pid != &init_struct_pid) { > - pid = alloc_pid(p->nsproxy->pid_ns_for_children); > + if (args->set_tid && !ns_capable( > + p->nsproxy->pid_ns_for_children->user_ns, > + CAP_SYS_ADMIN)) { > + retval = -EPERM; > + goto bad_fork_cleanup_thread; > + } > + pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid); copy_process() is already huge and complex, why not move this check into alloc_pid() ? Again, note that is accepts the same ->pid_ns_for_children. > @@ -166,6 +166,9 @@ struct pid *alloc_pid(struct pid_namespace *ns) > struct upid *upid; > int retval = -ENOMEM; > > + if (set_tid < 0 || set_tid >= pid_max) > + return ERR_PTR(-EINVAL); > + > pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); > if (!pid) > return ERR_PTR(retval); > @@ -186,12 +189,31 @@ struct pid *alloc_pid(struct pid_namespace *ns) > if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS) > pid_min = RESERVED_PIDS; > > - /* > - * Store a null pointer so find_pid_ns does not find > - * a partially initialized PID (see below). > - */ > - nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, > - pid_max, GFP_ATOMIC); > + if (set_tid) { > + /* > + * Also fail if a PID != 1 is requested > + * and no PID 1 exists. > + */ > + nr = -EINVAL; > + if (set_tid == 1 || !idr_is_empty(&tmp->idr)) On the second thought, I think we should check ns->child_reaper != NULL rather than !idr_is_empty(), this looks more robust and clean. And this way alloc_pid() can do everything lockless at the start, if (set_tid) { if (set_tid < 0 || set_tid >= pid_max) return ERR_PTR(-EINVAL); if (set_tid != 1 && !ns->child_reaper) return ERR_PTR(-EINVAL); if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); } and just for record... this is off-topic and I need to recheck, but today "ns->pid_allocated = 0" in free_pid() doesn't look right to me... This logic predates unshare(CLONE_PIDNS). Oleg.