* [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
@ 2016-12-13 6:39 Ingo Molnar
2016-12-13 12:18 ` Greg KH
0 siblings, 1 reply; 5+ messages in thread
From: Ingo Molnar @ 2016-12-13 6:39 UTC (permalink / raw)
To: stable kernel team; +Cc: Thomas Gleixner
hi Greg,
Please apply this fix to v4.9-stable as well, it's now upstream.
Thanks,
Ingo
----- Forwarded message from tip-bot for Michal Hocko <tipbot@zytor.com> -----
Date: Thu, 8 Dec 2016 01:13:24 -0800
From: tip-bot for Michal Hocko <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, tglx@linutronix.de, ddstreet@ieee.org, mhocko@suse.com, yuzhao@google.com, hpa@zytor.com
Subject: [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
Commit-ID: 777c6e0daebb3fcefbbd6f620410a946b07ef6d0
Gitweb: http://git.kernel.org/tip/777c6e0daebb3fcefbbd6f620410a946b07ef6d0
Author: Michal Hocko <mhocko@suse.com>
AuthorDate: Wed, 7 Dec 2016 14:54:38 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 8 Dec 2016 10:08:41 +0100
hotplug: Make register and unregister notifier API symmetric
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>
---
include/linux/cpu.h | 15 ++++-----------
kernel/cpu.c | 2 +-
2 files changed, 5 insertions(+), 12 deletions(-)
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index b886dc1..e571128 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -93,22 +93,16 @@ 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;
@@ -118,7 +112,6 @@ static inline int __register_cpu_notifier(struct notifier_block *nb)
{
return 0;
}
-#endif
static inline void unregister_cpu_notifier(struct notifier_block *nb)
{
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 29de1a9..217fd2e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -659,7 +659,6 @@ 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)
@@ -676,6 +675,7 @@ void __unregister_cpu_notifier(struct notifier_block *nb)
}
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
----- End forwarded message -----
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
2016-12-13 6:39 [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric Ingo Molnar
@ 2016-12-13 12:18 ` Greg KH
2016-12-13 20:50 ` Ingo Molnar
0 siblings, 1 reply; 5+ messages in thread
From: Greg KH @ 2016-12-13 12:18 UTC (permalink / raw)
To: Ingo Molnar; +Cc: stable kernel team, Thomas Gleixner
On Tue, Dec 13, 2016 at 07:39:58AM +0100, Ingo Molnar wrote:
>
> hi Greg,
>
> Please apply this fix to v4.9-stable as well, it's now upstream.
Ok, it looks like it belongs in older stable kernels as well, based on
the fixes: tag, correct?
thanks,
greg k-h
> ----- Forwarded message from tip-bot for Michal Hocko <tipbot@zytor.com> -----
>
> Date: Thu, 8 Dec 2016 01:13:24 -0800
> From: tip-bot for Michal Hocko <tipbot@zytor.com>
> To: linux-tip-commits@vger.kernel.org
> Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, tglx@linutronix.de, ddstreet@ieee.org, mhocko@suse.com, yuzhao@google.com, hpa@zytor.com
> Subject: [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
>
> Commit-ID: 777c6e0daebb3fcefbbd6f620410a946b07ef6d0
> Gitweb: http://git.kernel.org/tip/777c6e0daebb3fcefbbd6f620410a946b07ef6d0
> Author: Michal Hocko <mhocko@suse.com>
> AuthorDate: Wed, 7 Dec 2016 14:54:38 +0100
> Committer: Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Thu, 8 Dec 2016 10:08:41 +0100
>
> hotplug: Make register and unregister notifier API symmetric
>
> 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>
>
> ---
> include/linux/cpu.h | 15 ++++-----------
> kernel/cpu.c | 2 +-
> 2 files changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index b886dc1..e571128 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -93,22 +93,16 @@ 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;
> @@ -118,7 +112,6 @@ static inline int __register_cpu_notifier(struct notifier_block *nb)
> {
> return 0;
> }
> -#endif
>
> static inline void unregister_cpu_notifier(struct notifier_block *nb)
> {
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 29de1a9..217fd2e 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -659,7 +659,6 @@ 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)
> @@ -676,6 +675,7 @@ void __unregister_cpu_notifier(struct notifier_block *nb)
> }
> 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
>
> ----- End forwarded message -----
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@vger.kernel.org
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
2016-12-13 12:18 ` Greg KH
@ 2016-12-13 20:50 ` Ingo Molnar
2016-12-13 20:52 ` Thomas Gleixner
2016-12-13 22:25 ` Greg KH
0 siblings, 2 replies; 5+ messages in thread
From: Ingo Molnar @ 2016-12-13 20:50 UTC (permalink / raw)
To: Greg KH; +Cc: stable kernel team, Thomas Gleixner
* Greg KH <gregkh@linuxfoundation.org> wrote:
> On Tue, Dec 13, 2016 at 07:39:58AM +0100, Ingo Molnar wrote:
> >
> > hi Greg,
> >
> > Please apply this fix to v4.9-stable as well, it's now upstream.
>
> Ok, it looks like it belongs in older stable kernels as well, based on
> the fixes: tag, correct?
Yes, indeed - but the testing was v4.9 based and there's been all sorts of changes
in the CPU hotplug machinery.
The fixes tag:
> > Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU")
Suggests it's an ancient bug and 777c6e0daebb3fce cherry-picks fine as far back as
v4.6.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
2016-12-13 20:50 ` Ingo Molnar
@ 2016-12-13 20:52 ` Thomas Gleixner
2016-12-13 22:25 ` Greg KH
1 sibling, 0 replies; 5+ messages in thread
From: Thomas Gleixner @ 2016-12-13 20:52 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Greg KH, stable kernel team
On Tue, 13 Dec 2016, Ingo Molnar wrote:
> * Greg KH <gregkh@linuxfoundation.org> wrote:
>
> > On Tue, Dec 13, 2016 at 07:39:58AM +0100, Ingo Molnar wrote:
> > >
> > > hi Greg,
> > >
> > > Please apply this fix to v4.9-stable as well, it's now upstream.
> >
> > Ok, it looks like it belongs in older stable kernels as well, based on
> > the fixes: tag, correct?
>
> Yes, indeed - but the testing was v4.9 based and there's been all sorts of changes
> in the CPU hotplug machinery.
>
> The fixes tag:
>
> > > Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU")
>
> Suggests it's an ancient bug and 777c6e0daebb3fce cherry-picks fine as far back as
> v4.6.
Yes it's completely independent of the hotplug rework and should be backported.
Thanks,
tglx
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric
2016-12-13 20:50 ` Ingo Molnar
2016-12-13 20:52 ` Thomas Gleixner
@ 2016-12-13 22:25 ` Greg KH
1 sibling, 0 replies; 5+ messages in thread
From: Greg KH @ 2016-12-13 22:25 UTC (permalink / raw)
To: Ingo Molnar; +Cc: stable kernel team, Thomas Gleixner
On Tue, Dec 13, 2016 at 09:50:38PM +0100, Ingo Molnar wrote:
>
> * Greg KH <gregkh@linuxfoundation.org> wrote:
>
> > On Tue, Dec 13, 2016 at 07:39:58AM +0100, Ingo Molnar wrote:
> > >
> > > hi Greg,
> > >
> > > Please apply this fix to v4.9-stable as well, it's now upstream.
> >
> > Ok, it looks like it belongs in older stable kernels as well, based on
> > the fixes: tag, correct?
>
> Yes, indeed - but the testing was v4.9 based and there's been all sorts of changes
> in the CPU hotplug machinery.
>
> The fixes tag:
>
> > > Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU")
>
> Suggests it's an ancient bug and 777c6e0daebb3fce cherry-picks fine as far back as
> v4.6.
As 47e627bc8c9a was in 2.6.21, I did the trivial fixup and applied it to
4.4-stable as well.
thanks,
greg k-h
^ permalink raw reply [flat|nested] 5+ messages in thread
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2016-12-13 6:39 [tip:smp/urgent] hotplug: Make register and unregister notifier API symmetric Ingo Molnar
2016-12-13 12:18 ` Greg KH
2016-12-13 20:50 ` Ingo Molnar
2016-12-13 20:52 ` Thomas Gleixner
2016-12-13 22:25 ` Greg KH
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