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* [PATCH] mm, vmstat: Make sure mutex is a global static
@ 2017-11-07 21:38 Kees Cook
  2017-11-08  7:43 ` Vlastimil Babka
  2017-11-09  1:10 ` kemi
  0 siblings, 2 replies; 6+ messages in thread
From: Kees Cook @ 2017-11-07 21:38 UTC (permalink / raw)
  To: Andrew Morton, Jesper Dangaard Brouer
  Cc: Dave Hansen, Ying Huang, Vlastimil Babka, Michal Hocko, linux-kernel

The mutex in sysctl_vm_numa_stat_handler() needs to be a global static, not
a stack variable, otherwise it doesn't serve any purpose. Also, reading the
file with CONFIG_LOCKDEP=y will complain:

[   63.258593] INFO: trying to register non-static key.
[   63.259113] the code is fine but needs lockdep annotation.
[   63.259596] turning off the locking correctness validator.
[   63.260073] CPU: 1 PID: 4102 Comm: perl Not tainted 4.14.0-rc8-next-20171107+ #419
[   63.260769] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[   63.261570] Call Trace:
[   63.261783]  dump_stack+0x5f/0x86
[   63.262062]  register_lock_class+0xe4/0x550
[   63.262408]  ? __lock_acquire+0x308/0x1170
[   63.262746]  __lock_acquire+0x7e/0x1170
[   63.263063]  lock_acquire+0x9d/0x1d0
[   63.263363]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
[   63.263777]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
[   63.264192]  __mutex_lock+0xb8/0x9a0
[   63.264488]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
[   63.264942]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
[   63.265398]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
[   63.265840]  sysctl_vm_numa_stat_handler+0x8f/0x2d0
[   63.266270]  proc_sys_call_handler+0xe3/0x100
[   63.266655]  __vfs_read+0x33/0x1b0
[   63.266957]  vfs_read+0xa6/0x150
[   63.267244]  SyS_read+0x55/0xc0
[   63.267525]  do_syscall_64+0x56/0x140
[   63.267850]  entry_SYSCALL64_slow_path+0x25/0x25

Fixes: 920d5f77d1a25 ("mm, sysctl: make NUMA stats configurable")
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ying Huang <ying.huang@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 mm/vmstat.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index e0593434fd58..40b2db6db6b1 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -72,11 +72,12 @@ static void invalid_numa_statistics(void)
 	zero_global_numa_counters();
 }
 
+static DEFINE_MUTEX(vm_numa_stat_lock);
+
 int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *length, loff_t *ppos)
 {
 	int ret, oldval;
-	DEFINE_MUTEX(vm_numa_stat_lock);
 
 	mutex_lock(&vm_numa_stat_lock);
 	if (write)
-- 
2.7.4


-- 
Kees Cook
Pixel Security

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] mm, vmstat: Make sure mutex is a global static
  2017-11-07 21:38 [PATCH] mm, vmstat: Make sure mutex is a global static Kees Cook
@ 2017-11-08  7:43 ` Vlastimil Babka
  2017-11-08 14:20   ` Michal Hocko
  2017-11-08 15:21   ` Kees Cook
  2017-11-09  1:10 ` kemi
  1 sibling, 2 replies; 6+ messages in thread
From: Vlastimil Babka @ 2017-11-08  7:43 UTC (permalink / raw)
  To: Kees Cook, Andrew Morton, Jesper Dangaard Brouer
  Cc: Dave Hansen, Ying Huang, Michal Hocko, linux-kernel

On 11/07/2017 10:38 PM, Kees Cook wrote:
> The mutex in sysctl_vm_numa_stat_handler() needs to be a global static, not
> a stack variable, otherwise it doesn't serve any purpose. Also, reading the
> file with CONFIG_LOCKDEP=y will complain:

Oops, good catch.

> [   63.258593] INFO: trying to register non-static key.
> [   63.259113] the code is fine but needs lockdep annotation.
> [   63.259596] turning off the locking correctness validator.
> [   63.260073] CPU: 1 PID: 4102 Comm: perl Not tainted 4.14.0-rc8-next-20171107+ #419
> [   63.260769] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
> [   63.261570] Call Trace:
> [   63.261783]  dump_stack+0x5f/0x86
> [   63.262062]  register_lock_class+0xe4/0x550
> [   63.262408]  ? __lock_acquire+0x308/0x1170
> [   63.262746]  __lock_acquire+0x7e/0x1170
> [   63.263063]  lock_acquire+0x9d/0x1d0
> [   63.263363]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.263777]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.264192]  __mutex_lock+0xb8/0x9a0
> [   63.264488]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.264942]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.265398]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.265840]  sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.266270]  proc_sys_call_handler+0xe3/0x100
> [   63.266655]  __vfs_read+0x33/0x1b0
> [   63.266957]  vfs_read+0xa6/0x150
> [   63.267244]  SyS_read+0x55/0xc0
> [   63.267525]  do_syscall_64+0x56/0x140
> [   63.267850]  entry_SYSCALL64_slow_path+0x25/0x25
> 
> Fixes: 920d5f77d1a25 ("mm, sysctl: make NUMA stats configurable")

Note that this hash is specific to particular next-$DATE as mmotm is
reimported each day.

> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Ying Huang <ying.huang@intel.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  mm/vmstat.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index e0593434fd58..40b2db6db6b1 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -72,11 +72,12 @@ static void invalid_numa_statistics(void)
>  	zero_global_numa_counters();
>  }
>  
> +static DEFINE_MUTEX(vm_numa_stat_lock);
> +
>  int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
>  		void __user *buffer, size_t *length, loff_t *ppos)
>  {
>  	int ret, oldval;
> -	DEFINE_MUTEX(vm_numa_stat_lock);

Yeah it was Michal who suggested scoping the mutex here instead of
global scope, but I think he didn't mean to remove the 'static'
qualifier, and we both missed that in the review :(
So the scope under sysctl_vm_numa_stat_handler() should be okay, just
with the 'static' added.

>  
>  	mutex_lock(&vm_numa_stat_lock);
>  	if (write)
> 

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] mm, vmstat: Make sure mutex is a global static
  2017-11-08  7:43 ` Vlastimil Babka
@ 2017-11-08 14:20   ` Michal Hocko
  2017-11-08 15:21   ` Kees Cook
  1 sibling, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2017-11-08 14:20 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: Kees Cook, Andrew Morton, Jesper Dangaard Brouer, Dave Hansen,
	Ying Huang, linux-kernel

On Wed 08-11-17 08:43:44, Vlastimil Babka wrote:
> On 11/07/2017 10:38 PM, Kees Cook wrote:
[...]
> > +static DEFINE_MUTEX(vm_numa_stat_lock);
> > +
> >  int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
> >  		void __user *buffer, size_t *length, loff_t *ppos)
> >  {
> >  	int ret, oldval;
> > -	DEFINE_MUTEX(vm_numa_stat_lock);
> 
> Yeah it was Michal who suggested scoping the mutex here instead of
> global scope, but I think he didn't mean to remove the 'static'
> qualifier, and we both missed that in the review :(
> So the scope under sysctl_vm_numa_stat_handler() should be okay, just
> with the 'static' added.

exactly! Sorry that I've missed the missing static and thanks for
catching that Kees.

-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] mm, vmstat: Make sure mutex is a global static
  2017-11-08  7:43 ` Vlastimil Babka
  2017-11-08 14:20   ` Michal Hocko
@ 2017-11-08 15:21   ` Kees Cook
  2017-11-09  7:50     ` Michal Hocko
  1 sibling, 1 reply; 6+ messages in thread
From: Kees Cook @ 2017-11-08 15:21 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: Andrew Morton, Jesper Dangaard Brouer, Dave Hansen, Ying Huang,
	Michal Hocko, LKML

On Tue, Nov 7, 2017 at 11:43 PM, Vlastimil Babka <vbabka@suse.cz> wrote:
> On 11/07/2017 10:38 PM, Kees Cook wrote:
>> The mutex in sysctl_vm_numa_stat_handler() needs to be a global static, not
>> a stack variable, otherwise it doesn't serve any purpose. Also, reading the
>> file with CONFIG_LOCKDEP=y will complain:
>
> Oops, good catch.
>
>> [   63.258593] INFO: trying to register non-static key.
>> [   63.259113] the code is fine but needs lockdep annotation.
>> [   63.259596] turning off the locking correctness validator.
>> [   63.260073] CPU: 1 PID: 4102 Comm: perl Not tainted 4.14.0-rc8-next-20171107+ #419
>> [   63.260769] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
>> [   63.261570] Call Trace:
>> [   63.261783]  dump_stack+0x5f/0x86
>> [   63.262062]  register_lock_class+0xe4/0x550
>> [   63.262408]  ? __lock_acquire+0x308/0x1170
>> [   63.262746]  __lock_acquire+0x7e/0x1170
>> [   63.263063]  lock_acquire+0x9d/0x1d0
>> [   63.263363]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
>> [   63.263777]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
>> [   63.264192]  __mutex_lock+0xb8/0x9a0
>> [   63.264488]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
>> [   63.264942]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
>> [   63.265398]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
>> [   63.265840]  sysctl_vm_numa_stat_handler+0x8f/0x2d0
>> [   63.266270]  proc_sys_call_handler+0xe3/0x100
>> [   63.266655]  __vfs_read+0x33/0x1b0
>> [   63.266957]  vfs_read+0xa6/0x150
>> [   63.267244]  SyS_read+0x55/0xc0
>> [   63.267525]  do_syscall_64+0x56/0x140
>> [   63.267850]  entry_SYSCALL64_slow_path+0x25/0x25
>>
>> Fixes: 920d5f77d1a25 ("mm, sysctl: make NUMA stats configurable")
>
> Note that this hash is specific to particular next-$DATE as mmotm is
> reimported each day.

Ah yes, duh. :)

>
>> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: Ying Huang <ying.huang@intel.com>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>>  mm/vmstat.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/vmstat.c b/mm/vmstat.c
>> index e0593434fd58..40b2db6db6b1 100644
>> --- a/mm/vmstat.c
>> +++ b/mm/vmstat.c
>> @@ -72,11 +72,12 @@ static void invalid_numa_statistics(void)
>>       zero_global_numa_counters();
>>  }
>>
>> +static DEFINE_MUTEX(vm_numa_stat_lock);
>> +
>>  int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
>>               void __user *buffer, size_t *length, loff_t *ppos)
>>  {
>>       int ret, oldval;
>> -     DEFINE_MUTEX(vm_numa_stat_lock);
>
> Yeah it was Michal who suggested scoping the mutex here instead of
> global scope, but I think he didn't mean to remove the 'static'
> qualifier, and we both missed that in the review :(
> So the scope under sysctl_vm_numa_stat_handler() should be okay, just
> with the 'static' added.

That part is a matter of taste, I guess. :) But yes, static is important.

-Kees

-- 
Kees Cook
Pixel Security

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: mm, vmstat: Make sure mutex is a global static
  2017-11-07 21:38 [PATCH] mm, vmstat: Make sure mutex is a global static Kees Cook
  2017-11-08  7:43 ` Vlastimil Babka
@ 2017-11-09  1:10 ` kemi
  1 sibling, 0 replies; 6+ messages in thread
From: kemi @ 2017-11-09  1:10 UTC (permalink / raw)
  To: Kees Cook, Andrew Morton, Jesper Dangaard Brouer
  Cc: Dave Hansen, Ying Huang, Vlastimil Babka, Michal Hocko, linux-kernel



On 2017年11月08日 05:38, Kees Cook wrote:
> The mutex in sysctl_vm_numa_stat_handler() needs to be a global static, not
> a stack variable, otherwise it doesn't serve any purpose. Also, reading the
> file with CONFIG_LOCKDEP=y will complain:
> 

It's my mistake. Kees, thanks for catching it.

> [   63.258593] INFO: trying to register non-static key.
> [   63.259113] the code is fine but needs lockdep annotation.
> [   63.259596] turning off the locking correctness validator.
> [   63.260073] CPU: 1 PID: 4102 Comm: perl Not tainted 4.14.0-rc8-next-20171107+ #419
> [   63.260769] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
> [   63.261570] Call Trace:
> [   63.261783]  dump_stack+0x5f/0x86
> [   63.262062]  register_lock_class+0xe4/0x550
> [   63.262408]  ? __lock_acquire+0x308/0x1170
> [   63.262746]  __lock_acquire+0x7e/0x1170
> [   63.263063]  lock_acquire+0x9d/0x1d0
> [   63.263363]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.263777]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.264192]  __mutex_lock+0xb8/0x9a0
> [   63.264488]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.264942]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.265398]  ? sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.265840]  sysctl_vm_numa_stat_handler+0x8f/0x2d0
> [   63.266270]  proc_sys_call_handler+0xe3/0x100
> [   63.266655]  __vfs_read+0x33/0x1b0
> [   63.266957]  vfs_read+0xa6/0x150
> [   63.267244]  SyS_read+0x55/0xc0
> [   63.267525]  do_syscall_64+0x56/0x140
> [   63.267850]  entry_SYSCALL64_slow_path+0x25/0x25
> 
> Fixes: 920d5f77d1a25 ("mm, sysctl: make NUMA stats configurable")
> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Ying Huang <ying.huang@intel.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  mm/vmstat.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index e0593434fd58..40b2db6db6b1 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -72,11 +72,12 @@ static void invalid_numa_statistics(void)
>  	zero_global_numa_counters();
>  }
>  
> +static DEFINE_MUTEX(vm_numa_stat_lock);
> +
>  int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
>  		void __user *buffer, size_t *length, loff_t *ppos)
>  {
>  	int ret, oldval;
> -	DEFINE_MUTEX(vm_numa_stat_lock);
>  
>  	mutex_lock(&vm_numa_stat_lock);
>  	if (write)
> 

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] mm, vmstat: Make sure mutex is a global static
  2017-11-08 15:21   ` Kees Cook
@ 2017-11-09  7:50     ` Michal Hocko
  0 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2017-11-09  7:50 UTC (permalink / raw)
  To: Kees Cook
  Cc: Vlastimil Babka, Andrew Morton, Jesper Dangaard Brouer,
	Dave Hansen, Ying Huang, LKML

On Wed 08-11-17 07:21:20, Kees Cook wrote:
> On Tue, Nov 7, 2017 at 11:43 PM, Vlastimil Babka <vbabka@suse.cz> wrote:
> > On 11/07/2017 10:38 PM, Kees Cook wrote:
[...]
> >> +static DEFINE_MUTEX(vm_numa_stat_lock);
> >> +
> >>  int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
> >>               void __user *buffer, size_t *length, loff_t *ppos)
> >>  {
> >>       int ret, oldval;
> >> -     DEFINE_MUTEX(vm_numa_stat_lock);
> >
> > Yeah it was Michal who suggested scoping the mutex here instead of
> > global scope, but I think he didn't mean to remove the 'static'
> > qualifier, and we both missed that in the review :(
> > So the scope under sysctl_vm_numa_stat_handler() should be okay, just
> > with the 'static' added.
> 
> That part is a matter of taste, I guess. :) But yes, static is important.

The primary reason I prefer function scope lock is that it is less
tempting to reuse the lock for something else that way. But this is
hardly something to insist on. So I am ok with the file scope as well.
-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2017-11-09  7:50 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-11-07 21:38 [PATCH] mm, vmstat: Make sure mutex is a global static Kees Cook
2017-11-08  7:43 ` Vlastimil Babka
2017-11-08 14:20   ` Michal Hocko
2017-11-08 15:21   ` Kees Cook
2017-11-09  7:50     ` Michal Hocko
2017-11-09  1:10 ` kemi

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