From nobody Tue Jun 30 08:12:31 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8307DC433F5 for ; Fri, 21 Jan 2022 10:12:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379939AbiAUKMf (ORCPT ); Fri, 21 Jan 2022 05:12:35 -0500 Received: from szxga02-in.huawei.com ([45.249.212.188]:30292 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379952AbiAUKM3 (ORCPT ); Fri, 21 Jan 2022 05:12:29 -0500 Received: from dggpeml500023.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4JgFXY1yCCzbcvX; Fri, 21 Jan 2022 18:11:41 +0800 (CST) Received: from dggpeml500018.china.huawei.com (7.185.36.186) by dggpeml500023.china.huawei.com (7.185.36.114) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Fri, 21 Jan 2022 18:12:27 +0800 Received: from huawei.com (10.67.174.153) by dggpeml500018.china.huawei.com (7.185.36.186) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Fri, 21 Jan 2022 18:12:27 +0800 From: Zhang Qiao To: , CC: , , , , , , , , , , Subject: [PATCH] cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug Date: Fri, 21 Jan 2022 18:12:10 +0800 Message-ID: <20220121101210.84926-1-zhangqiao22@huawei.com> X-Mailer: git-send-email 2.18.0.huawei.25 MIME-Version: 1.0 X-Originating-IP: [10.67.174.153] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500018.china.huawei.com (7.185.36.186) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As previously discussed(https://lkml.org/lkml/2022/1/20/51), cpuset_attach() is affected with similar cpu hotplug race, as follow scenario: cpuset_attach() cpu hotplug --------------------------- ---------------------- down_write(cpuset_rwsem) guarantee_online_cpus() // (load cpus_attach) sched_cpu_deactivate set_cpu_active() // will change cpu_active_mask set_cpus_allowed_ptr(cpus_attach) __set_cpus_allowed_ptr_locked() // (if the intersection of cpus_attach and cpu_active_mask is empty, will return -EINVAL) up_write(cpuset_rwsem) To avoid races such as described above, protect cpuset_attach() call with cpu_hotplug_lock. Fixes: be367d099270 ("cgroups: let ss->can_attach and ss->attach do whole t= hreadgroups at a time") Reported-by: Zhao Gongyi Signed-off-by: Zhang Qiao Acked-by: Waiman Long Reviewed-by: Michal Koutn=C3=BD --- kernel/cgroup/cpuset.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index dc653ab26e50..0af5725cc1df 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2252,6 +2252,7 @@ static void cpuset_attach(struct cgroup_taskset *tset) cgroup_taskset_first(tset, &css); cs =3D css_cs(css); + cpus_read_lock(); percpu_down_write(&cpuset_rwsem); guarantee_online_mems(cs, &cpuset_attach_nodemask_to); @@ -2305,6 +2306,7 @@ static void cpuset_attach(struct cgroup_taskset *tset) wake_up(&cpuset_attach_wq); percpu_up_write(&cpuset_rwsem); + cpus_read_unlock(); } /* The various types of files and directories in a cpuset file system */ -- 2.18.0