From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:44418 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933864AbcLMPbq (ORCPT ); Tue, 13 Dec 2016 10:31:46 -0500 Subject: Patch "hotplug: Make register and unregister notifier API symmetric" has been added to the 4.8-stable tree To: mhocko@suse.com, akpm@linux-foundation.org, ddstreet@ieee.org, gregkh@linuxfoundation.org, tglx@linutronix.de, yuzhao@google.com Cc: , From: Date: Tue, 13 Dec 2016 07:25:26 -0800 Message-ID: <1481642726116119@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled hotplug: Make register and unregister notifier API symmetric to the 4.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: hotplug-make-register-and-unregister-notifier-api-symmetric.patch and it can be found in the queue-4.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 777c6e0daebb3fcefbbd6f620410a946b07ef6d0 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 7 Dec 2016 14:54:38 +0100 Subject: hotplug: Make register and unregister notifier API symmetric From: Michal Hocko commit 777c6e0daebb3fcefbbd6f620410a946b07ef6d0 upstream. Yu Zhao has noticed that __unregister_cpu_notifier only unregisters its notifiers when HOTPLUG_CPU=y while the registration might succeed even when HOTPLUG_CPU=n if MODULE is enabled. This means that e.g. zswap might keep a stale notifier on the list on the manual clean up during the pool tear down and thus corrupt the list. Resulting in the following [ 144.964346] BUG: unable to handle kernel paging request at ffff880658a2be78 [ 144.971337] IP: [] raw_notifier_chain_register+0x1b/0x40 [ 145.122628] Call Trace: [ 145.125086] [] __register_cpu_notifier+0x18/0x20 [ 145.131350] [] zswap_pool_create+0x273/0x400 [ 145.137268] [] __zswap_param_set+0x1fc/0x300 [ 145.143188] [] ? trace_hardirqs_on+0xd/0x10 [ 145.149018] [] ? kernel_param_lock+0x28/0x30 [ 145.154940] [] ? __might_fault+0x4f/0xa0 [ 145.160511] [] zswap_compressor_param_set+0x17/0x20 [ 145.167035] [] param_attr_store+0x5c/0xb0 [ 145.172694] [] module_attr_store+0x1d/0x30 [ 145.178443] [] sysfs_kf_write+0x4f/0x70 [ 145.183925] [] kernfs_fop_write+0x149/0x180 [ 145.189761] [] __vfs_write+0x18/0x40 [ 145.194982] [] vfs_write+0xb2/0x1a0 [ 145.200122] [] SyS_write+0x52/0xa0 [ 145.205177] [] entry_SYSCALL_64_fastpath+0x12/0x17 This can be even triggered manually by changing /sys/module/zswap/parameters/compressor multiple times. Fix this issue by making unregister APIs symmetric to the register so there are no surprises. Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU") Reported-and-tested-by: Yu Zhao Signed-off-by: Michal Hocko Cc: linux-mm@kvack.org Cc: Andrew Morton Cc: Dan Streetman Link: http://lkml.kernel.org/r/20161207135438.4310-1-mhocko@kernel.org Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- include/linux/cpu.h | 15 ++++----------- kernel/cpu.c | 2 +- 2 files changed, 5 insertions(+), 12 deletions(-) --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -105,22 +105,16 @@ extern bool cpuhp_tasks_frozen; { .notifier_call = fn, .priority = pri }; \ __register_cpu_notifier(&fn##_nb); \ } -#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */ -#define cpu_notifier(fn, pri) do { (void)(fn); } while (0) -#define __cpu_notifier(fn, pri) do { (void)(fn); } while (0) -#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */ -#ifdef CONFIG_HOTPLUG_CPU extern int register_cpu_notifier(struct notifier_block *nb); extern int __register_cpu_notifier(struct notifier_block *nb); extern void unregister_cpu_notifier(struct notifier_block *nb); extern void __unregister_cpu_notifier(struct notifier_block *nb); -#else -#ifndef MODULE -extern int register_cpu_notifier(struct notifier_block *nb); -extern int __register_cpu_notifier(struct notifier_block *nb); -#else +#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */ +#define cpu_notifier(fn, pri) do { (void)(fn); } while (0) +#define __cpu_notifier(fn, pri) do { (void)(fn); } while (0) + static inline int register_cpu_notifier(struct notifier_block *nb) { return 0; @@ -130,7 +124,6 @@ static inline int __register_cpu_notifie { return 0; } -#endif static inline void unregister_cpu_notifier(struct notifier_block *nb) { --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -578,7 +578,6 @@ void __init cpuhp_threads_init(void) kthread_unpark(this_cpu_read(cpuhp_state.thread)); } -#ifdef CONFIG_HOTPLUG_CPU EXPORT_SYMBOL(register_cpu_notifier); EXPORT_SYMBOL(__register_cpu_notifier); void unregister_cpu_notifier(struct notifier_block *nb) @@ -595,6 +594,7 @@ void __unregister_cpu_notifier(struct no } EXPORT_SYMBOL(__unregister_cpu_notifier); +#ifdef CONFIG_HOTPLUG_CPU /** * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU * @cpu: a CPU id Patches currently in stable-queue which might be from mhocko@suse.com are queue-4.8/hotplug-make-register-and-unregister-notifier-api-symmetric.patch