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[PATCH 4.8 32/33] hotplug: Make register and unregister notifier API symmetric

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.8 32/33] hotplug: Make register and unregister notifier API symmetric
Date 2016-12-13 18:20 +0100
Message-ID <sNYUa-3UP-43@gated-at.bofh.it> (permalink)
References <sNYU9-3UP-11@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michal Hocko <mhocko@suse.com>

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: [<ffffffffa290b00b>] raw_notifier_chain_register+0x1b/0x40
<snipped>
[  145.122628] Call Trace:
[  145.125086]  [<ffffffffa28e5cf8>] __register_cpu_notifier+0x18/0x20
[  145.131350]  [<ffffffffa2a5dd73>] zswap_pool_create+0x273/0x400
[  145.137268]  [<ffffffffa2a5e0fc>] __zswap_param_set+0x1fc/0x300
[  145.143188]  [<ffffffffa2944c1d>] ? trace_hardirqs_on+0xd/0x10
[  145.149018]  [<ffffffffa2908798>] ? kernel_param_lock+0x28/0x30
[  145.154940]  [<ffffffffa2a3e8cf>] ? __might_fault+0x4f/0xa0
[  145.160511]  [<ffffffffa2a5e237>] zswap_compressor_param_set+0x17/0x20
[  145.167035]  [<ffffffffa2908d3c>] param_attr_store+0x5c/0xb0
[  145.172694]  [<ffffffffa290848d>] module_attr_store+0x1d/0x30
[  145.178443]  [<ffffffffa2b2b41f>] sysfs_kf_write+0x4f/0x70
[  145.183925]  [<ffffffffa2b2a5b9>] kernfs_fop_write+0x149/0x180
[  145.189761]  [<ffffffffa2a99248>] __vfs_write+0x18/0x40
[  145.194982]  [<ffffffffa2a9a412>] vfs_write+0xb2/0x1a0
[  145.200122]  [<ffffffffa2a9a732>] SyS_write+0x52/0xa0
[  145.205177]  [<ffffffffa2ff4d97>] 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 <yuzhao@google.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Link: http://lkml.kernel.org/r/20161207135438.4310-1-mhocko@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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

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Thread

[PATCH 4.8 00/33] 4.8.15-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 20/33] crypto: marvell - Dont copy hash operation twice into the SRAM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 33/33] crypto: rsa - Add Makefile dependencies to fix parallel builds Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 32/33] hotplug: Make register and unregister notifier API symmetric Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 02/33] powerpc/mm: Fix lazy icache flush on pre-POWER5 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 17/33] acpi, nfit, libnvdimm: fix / harden ars_status output length handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 28/33] ARM: dts: imx7d: fix LCDIF clock assignment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 30/33] m68k: Fix ndelay() macro Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 31/33] batman-adv: Check for alloc errors when preparing TT local data Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:20 +0100
  [PATCH 4.8 05/33] parisc: Purge TLB before setting PTE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 10/33] locking/rtmutex: Use READ_ONCE() in rt_mutex_owner() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 22/33] crypto: mcryptd - Check mcryptd algorithm compatibility Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 06/33] parisc: Remove unnecessary TLB purges from flush_dcache_page_asm and flush_icache_page_asm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 16/33] acpi, nfit: fix extended status translations for ACPI DSMs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 14/33] vhost-vsock: fix orphan connection reset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 04/33] fuse: fix clearing suid, sgid for chown() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 23/33] crypto: marvell - Dont corrupt state of an STD req for re-stepped ahash Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 08/33] zram: restrict add/remove attributes to root only Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 07/33] parisc: Fix TLB related boot crash on SMP machines Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 15/33] perf/x86: Fix full width counter, counter overflow Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 11/33] device-dax: fix private mapping restriction, permit read-only Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 09/33] locking/rtmutex: Prevent dequeue vs. unlock race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 18/33] acpi, nfit: validate ars_status output buffer size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 13/33] sched/autogroup: Fix 64-bit kernel nice level adjustment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 26/33] Revert "ACPI: Execute _PTS before system reboot" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 03/33] powerpc/boot: Fix build failure in 32-bit boot wrapper Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 12/33] scsi: lpfc: fix oops/BUG in lpfc_sli_ringtxcmpl_put() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  [PATCH 4.8 24/33] can: raw: raw_setsockopt: limit number of can_filter that can be set Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 18:30 +0100
  Re: [PATCH 4.8 00/33] 4.8.15-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-12-13 20:40 +0100
    Re: [PATCH 4.8 00/33] 4.8.15-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-13 21:10 +0100
  Re: [PATCH 4.8 00/33] 4.8.15-stable review Guenter Roeck <linux@roeck-us.net> - 2016-12-14 05:20 +0100
    Re: [PATCH 4.8 00/33] 4.8.15-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-14 13:50 +0100

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