Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752984AbdHIQxs (ORCPT ); Wed, 9 Aug 2017 12:53:48 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38638 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752875AbdHIQxm (ORCPT ); Wed, 9 Aug 2017 12:53:42 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo Subject: [PATCH 4.12 007/106] cgroup: create dfl_root files on subsys registration Date: Wed, 9 Aug 2017 09:51:51 -0700 Message-Id: <20170809164516.841296295@linuxfoundation.org> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170809164515.714288642@linuxfoundation.org> References: <20170809164515.714288642@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1474 Lines: 45 4.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit 7af608e4f9530372aec6e940552bf76595f2e265 upstream. On subsystem registration, css_populate_dir() is not called on the new root css, so the interface files for the subsystem on cgrp_dfl_root aren't created on registration. This is a residue from the days when cgrp_dfl_root was used only as the parking spot for unused subsystems, which no longer is true as it's used as the root for cgroup2. This is often fine as later operations tend to create them as a part of mount (cgroup1) or subtree_control operations (cgroup2); however, it's not difficult to mount cgroup2 with the controller interface files missing as Waiman found out. Fix it by invoking css_populate_dir() on the root css on subsys registration. Signed-off-by: Tejun Heo Reported-and-tested-by: Waiman Long Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup/cgroup.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4578,6 +4578,10 @@ int __init cgroup_init(void) if (ss->bind) ss->bind(init_css_set.subsys[ssid]); + + mutex_lock(&cgroup_mutex); + css_populate_dir(init_css_set.subsys[ssid]); + mutex_unlock(&cgroup_mutex); } /* init_css_set.subsys[] has been updated, re-hash */