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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 EAD1EC2D0CE for ; Tue, 21 Jan 2020 15:50:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5AFD207E0 for ; Tue, 21 Jan 2020 15:50:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729256AbgAUPub (ORCPT ); Tue, 21 Jan 2020 10:50:31 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:39892 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726714AbgAUPua (ORCPT ); Tue, 21 Jan 2020 10:50:30 -0500 Received: from [154.119.55.246] (helo=localhost.localdomain) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1itvnP-0004D0-6S; Tue, 21 Jan 2020 15:50:27 +0000 From: Christian Brauner To: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo Cc: Oleg Nesterov , Christian Brauner , Li Zefan , Johannes Weiner , cgroups@vger.kernel.org Subject: [PATCH v5 1/6] cgroup: unify attach permission checking Date: Tue, 21 Jan 2020 16:48:39 +0100 Message-Id: <20200121154844.411-2-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200121154844.411-1-christian.brauner@ubuntu.com> References: <20200121154844.411-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- /* v1 */ Link: https://lore.kernel.org/r/20191218173516.7875-2-christian.brauner@ubuntu.com /* v2 */ Link: https://lore.kernel.org/r/20191223061504.28716-2-christian.brauner@ubuntu.com - Christian Brauner : - Fix return value of cgroup_attach_permissions. It used to return 0 when it should've returned -EOPNOTSUPP. - Fix call to cgroup_attach_permissions() in cgroup_procs_write(). It accidently specified that a thread was moved causing an additional check for domain-group equality to be executed that is not needed. /* v3 */ Link: https://lore.kernel.org/r/20200117002143.15559-2-christian.brauner@ubuntu.com unchanged /* v4 */ Link: https://lore.kernel.org/r/20200117181219.14542-2-christian.brauner@ubuntu.com unchanged /* v5 */ unchanged --- kernel/cgroup/cgroup.c | 39 +++++++++++++++++++++++++-------------- 1 file changed, 25 insertions(+), 14 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 735af8f15f95..7b98cc389dae 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 +4686,26 @@ static int cgroup_procs_write_permission(struct cgroup *src_cgrp, return 0; } +static int cgroup_attach_permissions(struct cgroup *src_cgrp, + struct cgroup *dst_cgrp, + struct super_block *sb, bool thread) +{ + int ret = 0; + + 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 && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp)) + ret = -EOPNOTSUPP; + + return ret; +} + static ssize_t cgroup_procs_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { @@ -4712,8 +4728,8 @@ 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, false); if (ret) goto out_finish; @@ -4757,16 +4773,11 @@ static ssize_t cgroup_threads_write(struct kernfs_open_file *of, spin_unlock_irq(&css_set_lock); /* thread migrations follow the cgroup.procs delegation rule */ - 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); if (ret) goto out_finish; - /* and must be contained in the same domain */ - ret = -EOPNOTSUPP; - if (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp) - goto out_finish; - ret = cgroup_attach_task(dst_cgrp, task, false); out_finish: -- 2.25.0