From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754934AbbAWKh1 (ORCPT ); Fri, 23 Jan 2015 05:37:27 -0500 Received: from terminus.zytor.com ([198.137.202.10]:36158 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754528AbbAWKhX (ORCPT ); Fri, 23 Jan 2015 05:37:23 -0500 Date: Fri, 23 Jan 2015 02:36:29 -0800 From: tip-bot for Lai Jiangshan Message-ID: Cc: srivatsa.bhat@linux.vnet.ibm.com, rusty@rustcorp.com.au, laijs@cn.fujitsu.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, rientjes@google.com Reply-To: laijs@cn.fujitsu.com, rusty@rustcorp.com.au, tglx@linutronix.de, srivatsa.bhat@linux.vnet.ibm.com, mingo@kernel.org, peterz@infradead.org, rientjes@google.com, linux-kernel@vger.kernel.org, hpa@zytor.com In-Reply-To: <1406777421-12830-1-git-send-email-laijs@cn.fujitsu.com> References: <1406777421-12830-1-git-send-email-laijs@cn.fujitsu.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/urgent] smpboot: Add missing get_online_cpus() in smpboot_register_percpu_thread() Git-Commit-ID: 4bee96860a65c3a62d332edac331b3cf936ba3ad X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4bee96860a65c3a62d332edac331b3cf936ba3ad Gitweb: http://git.kernel.org/tip/4bee96860a65c3a62d332edac331b3cf936ba3ad Author: Lai Jiangshan AuthorDate: Thu, 31 Jul 2014 11:30:17 +0800 Committer: Thomas Gleixner CommitDate: Fri, 23 Jan 2015 11:33:51 +0100 smpboot: Add missing get_online_cpus() in smpboot_register_percpu_thread() The following race exists in the smpboot percpu threads management: CPU0 CPU1 cpu_up(2) get_online_cpus(); smpboot_create_threads(2); smpboot_register_percpu_thread(); for_each_online_cpu(); __smpboot_create_thread(); __cpu_up(2); This results in a missing per cpu thread for the newly onlined cpu2 and in a NULL pointer dereference on a consecutive offline of that cpu. Proctect smpboot_register_percpu_thread() with get_online_cpus() to prevent that. [ tglx: Massaged changelog and removed the change in smpboot_unregister_percpu_thread() because that's an optimization and therefor not stable material. ] Signed-off-by: Lai Jiangshan Cc: Thomas Gleixner Cc: Rusty Russell Cc: Peter Zijlstra Cc: Srivatsa S. Bhat Cc: David Rientjes Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1406777421-12830-1-git-send-email-laijs@cn.fujitsu.com Signed-off-by: Thomas Gleixner --- kernel/smpboot.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/smpboot.c b/kernel/smpboot.c index f032fb5..40190f2 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -280,6 +280,7 @@ int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread) unsigned int cpu; int ret = 0; + get_online_cpus(); mutex_lock(&smpboot_threads_lock); for_each_online_cpu(cpu) { ret = __smpboot_create_thread(plug_thread, cpu); @@ -292,6 +293,7 @@ int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread) list_add(&plug_thread->list, &hotplug_threads); out: mutex_unlock(&smpboot_threads_lock); + put_online_cpus(); return ret; } EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);