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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 D52FCC43603 for ; Wed, 18 Dec 2019 23:46:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AFC4A218AC for ; Wed, 18 Dec 2019 23:46:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726694AbfLRXqh (ORCPT ); Wed, 18 Dec 2019 18:46:37 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:50217 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725948AbfLRXqh (ORCPT ); Wed, 18 Dec 2019 18:46:37 -0500 Received: from [213.220.153.21] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1ihj1W-0008Pp-4V; Wed, 18 Dec 2019 23:46:34 +0000 Date: Thu, 19 Dec 2019 00:46:33 +0100 From: Christian Brauner To: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo Cc: Li Zefan , Johannes Weiner , cgroups@vger.kernel.org Subject: Re: [PATCH 1/3] cgroup: unify attach permission checking Message-ID: <20191218234632.3xpobnq6efprohal@wittgenstein> References: <20191218173516.7875-1-christian.brauner@ubuntu.com> <20191218173516.7875-2-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191218173516.7875-2-christian.brauner@ubuntu.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 18, 2019 at 06:35:14PM +0100, Christian Brauner wrote: > The core codepaths to check whether a process can be attached to a > cgroup are the same for threads and thread-group leaders. Only a small > piece of code verifying that source and destination cgroup are in the > same domain differentiates the thread permission checking from > thread-group leader permission checking. > Since cgroup_migrate_vet_dst() only matters cgroup2 - it is a noop on > cgroup1 - we can move it out of cgroup_attach_task(). > All checks can now be consolidated into a new helper > cgroup_attach_permissions() callable from both cgroup_procs_write() and > cgroup_threads_write(). > > Cc: Tejun Heo > Cc: Li Zefan > Cc: Johannes Weiner > Cc: cgroups@vger.kernel.org > Signed-off-by: Christian Brauner > --- > kernel/cgroup/cgroup.c | 46 +++++++++++++++++++++++++++++------------- > 1 file changed, 32 insertions(+), 14 deletions(-) > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index 735af8f15f95..5ee06c1f7456 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -2719,11 +2719,7 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader, > { > DEFINE_CGROUP_MGCTX(mgctx); > struct task_struct *task; > - int ret; > - > - ret = cgroup_migrate_vet_dst(dst_cgrp); > - if (ret) > - return ret; > + int ret = 0; > > /* look up all src csets */ > spin_lock_irq(&css_set_lock); > @@ -4690,6 +4686,33 @@ static int cgroup_procs_write_permission(struct cgroup *src_cgrp, > return 0; > } > > +static inline bool cgroup_same_domain(const struct cgroup *src_cgrp, > + const struct cgroup *dst_cgrp) > +{ > + return src_cgrp->dom_cgrp == dst_cgrp->dom_cgrp; > +} > + > +static int cgroup_attach_permissions(struct cgroup *src_cgrp, > + struct cgroup *dst_cgrp, > + struct super_block *sb, bool thread) > +{ > + int ret; > + > + ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb); > + if (ret) > + return ret; > + > + ret = cgroup_migrate_vet_dst(dst_cgrp); > + if (ret) > + return ret; > + > + if (thread && > + !cgroup_same_domain(src_cgrp->dom_cgrp, dst_cgrp->dom_cgrp)) > + ret = -EOPNOTSUPP; > + > + return 0; > +} > + > static ssize_t cgroup_procs_write(struct kernfs_open_file *of, > char *buf, size_t nbytes, loff_t off) > { > @@ -4712,8 +4735,8 @@ static ssize_t cgroup_procs_write(struct kernfs_open_file *of, > src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root); > spin_unlock_irq(&css_set_lock); > > - ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, > - of->file->f_path.dentry->d_sb); > + ret = cgroup_attach_permissions(src_cgrp, dst_cgrp, > + of->file->f_path.dentry->d_sb, true); typo: s/true/false/