[PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap

[PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap

[Liang He]

In opal_powercap_init(), of_find_compatible_node() will return
a node pointer with refcount incremented. We should use of_node_put()
in fail path or when it is not used anymore.

Besides, for_each_child_of_node() will automatically *inc* and *dec*
refcount during iteration. However, we should add the of_node_put()
if there is a break.

Signed-off-by: Liang He <windhl@126.com>
---
 arch/powerpc/platforms/powernv/opal-powercap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
index 64506b46e77b..b102477d3f95 100644
--- a/arch/powerpc/platforms/powernv/opal-powercap.c
+++ b/arch/powerpc/platforms/powernv/opal-powercap.c
@@ -153,7 +153,7 @@ void __init opal_powercap_init(void)
 	pcaps = kcalloc(of_get_child_count(powercap), sizeof(*pcaps),
 			GFP_KERNEL);
 	if (!pcaps)
-		return;
+		goto out_powercap;
 
 	powercap_kobj = kobject_create_and_add("powercap", opal_kobj);
 	if (!powercap_kobj) {
@@ -236,6 +236,9 @@ void __init opal_powercap_init(void)
 		kfree(pcaps[i].pg.name);
 	}
 	kobject_put(powercap_kobj);
+	of_node_put(node);
 out_pcaps:
 	kfree(pcaps);
+out_powercap:
+	of_node_put(powercap);
 }
-- 
2.25.1

Re: [PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap

[Christophe JAILLET]

Le 17/06/2022 à 06:20, Liang He a écrit :
> In opal_powercap_init(), of_find_compatible_node() will return
> a node pointer with refcount incremented. We should use of_node_put()
> in fail path or when it is not used anymore.
> 
> Besides, for_each_child_of_node() will automatically *inc* and *dec*
> refcount during iteration. However, we should add the of_node_put()
> if there is a break.

Hi,

I'm not sure that your patch is right here. Because of this *inc* and 
*dec* things, do we still need to of_node_put(powercap) once we have 
entered for_each_child_of_node?

I think that this reference will be released on the first iteration of 
the loop.


Maybe of_node_put(powercap) should be duplicated everywhere it is 
relevant and removed from the error handling path?
Or an additional reference should be taken before the loop?
Or adding a new label with "powercap = NULL" and branching there when 
needed?

CJ

> 
> Signed-off-by: Liang He <windhl@126.com>
> ---
>   arch/powerpc/platforms/powernv/opal-powercap.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
> index 64506b46e77b..b102477d3f95 100644
> --- a/arch/powerpc/platforms/powernv/opal-powercap.c
> +++ b/arch/powerpc/platforms/powernv/opal-powercap.c
> @@ -153,7 +153,7 @@ void __init opal_powercap_init(void)
>   	pcaps = kcalloc(of_get_child_count(powercap), sizeof(*pcaps),
>   			GFP_KERNEL);
>   	if (!pcaps)
> -		return;
> +		goto out_powercap;
>   
>   	powercap_kobj = kobject_create_and_add("powercap", opal_kobj);
>   	if (!powercap_kobj) {
> @@ -236,6 +236,9 @@ void __init opal_powercap_init(void)
>   		kfree(pcaps[i].pg.name);
>   	}
>   	kobject_put(powercap_kobj);
> +	of_node_put(node);
>   out_pcaps:
>   	kfree(pcaps);
> +out_powercap:
> +	of_node_put(powercap);
>   }

Re:Re: [PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap

[Liang He]

At 2022-06-17 13:01:27, "Christophe JAILLET" <christophe.jaillet@wanadoo.fr> wrote:
>Le 17/06/2022 à 06:20, Liang He a écrit :
>> In opal_powercap_init(), of_find_compatible_node() will return
>> a node pointer with refcount incremented. We should use of_node_put()
>> in fail path or when it is not used anymore.
>> 
>> Besides, for_each_child_of_node() will automatically *inc* and *dec*
>> refcount during iteration. However, we should add the of_node_put()
>> if there is a break.
>
>Hi,
>
>I'm not sure that your patch is right here. Because of this *inc* and 
>*dec* things, do we still need to of_node_put(powercap) once we have 
>entered for_each_child_of_node?
>
>I think that this reference will be released on the first iteration of 
>the loop.
>

Hi, CJ, 

Thanks for your reply and I want have a discuss.

Based on my review on the src of 'of_get_next_child',  there is only
*inc* for next and *dec* for pre as follow. 

(|node| == powercap)
======__of_get_next_child( |node|, prev)======
     ...
        next = prev? prev->sibling:|node|->child;
	of_node_get(next);
	of_node_put(prev);
     ...
=========================

However, there is no any code to release the |node| (i.e., *powercap*).

Am I right?   If I am wrong, please correct me, thanks.

>
>Maybe of_node_put(powercap) should be duplicated everywhere it is 
>relevant and removed from the error handling path?
>Or an additional reference should be taken before the loop?
>Or adding a new label with "powercap = NULL" and branching there when 
>needed?
>
>CJ

If my understanding is right, I think current patch is right.

Otherwise, I will make a new patch to handle that, Thanks.

Liang 

>
>> 
>> Signed-off-by: Liang He <windhl@126.com>
>> ---
>>   arch/powerpc/platforms/powernv/opal-powercap.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
>> index 64506b46e77b..b102477d3f95 100644
>> --- a/arch/powerpc/platforms/powernv/opal-powercap.c
>> +++ b/arch/powerpc/platforms/powernv/opal-powercap.c
>> @@ -153,7 +153,7 @@ void __init opal_powercap_init(void)
>>   	pcaps = kcalloc(of_get_child_count(powercap), sizeof(*pcaps),
>>   			GFP_KERNEL);
>>   	if (!pcaps)
>> -		return;
>> +		goto out_powercap;
>>   
>>   	powercap_kobj = kobject_create_and_add("powercap", opal_kobj);
>>   	if (!powercap_kobj) {
>> @@ -236,6 +236,9 @@ void __init opal_powercap_init(void)
>>   		kfree(pcaps[i].pg.name);
>>   	}
>>   	kobject_put(powercap_kobj);
>> +	of_node_put(node);
>>   out_pcaps:
>>   	kfree(pcaps);
>> +out_powercap:
>> +	of_node_put(powercap);
>>   }

Re:Re: [PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap

[Liang He]

At 2022-06-17 13:01:27, "Christophe JAILLET" <christophe.jaillet@wanadoo.fr> wrote:
>Le 17/06/2022 à 06:20, Liang He a écrit :
>> In opal_powercap_init(), of_find_compatible_node() will return
>> a node pointer with refcount incremented. We should use of_node_put()
>> in fail path or when it is not used anymore.
>> 
>> Besides, for_each_child_of_node() will automatically *inc* and *dec*
>> refcount during iteration. However, we should add the of_node_put()
>> if there is a break.
>
>Hi,
>
>I'm not sure that your patch is right here. Because of this *inc* and 
>*dec* things, do we still need to of_node_put(powercap) once we have 
>entered for_each_child_of_node?
>
>I think that this reference will be released on the first iteration of 
>the loop.
>
>
>Maybe of_node_put(powercap) should be duplicated everywhere it is 
>relevant and removed from the error handling path?
>Or an additional reference should be taken before the loop?
>Or adding a new label with "powercap = NULL" and branching there when 
>needed?
>
>CJ
>
>> 
>> Signed-off-by: Liang He <windhl@126.com>
>> ---
>>   arch/powerpc/platforms/powernv/opal-powercap.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
>> index 64506b46e77b..b102477d3f95 100644
>> --- a/arch/powerpc/platforms/powernv/opal-powercap.c
>> +++ b/arch/powerpc/platforms/powernv/opal-powercap.c
>> @@ -153,7 +153,7 @@ void __init opal_powercap_init(void)
>>   	pcaps = kcalloc(of_get_child_count(powercap), sizeof(*pcaps),
>>   			GFP_KERNEL);
>>   	if (!pcaps)
>> -		return;
>> +		goto out_powercap;
>>   
>>   	powercap_kobj = kobject_create_and_add("powercap", opal_kobj);
>>   	if (!powercap_kobj) {
>> @@ -236,6 +236,9 @@ void __init opal_powercap_init(void)
>>   		kfree(pcaps[i].pg.name);
>>   	}
>>   	kobject_put(powercap_kobj);
>> +	of_node_put(node);
>>   out_pcaps:
>>   	kfree(pcaps);
>> +out_powercap:
>> +	of_node_put(powercap);
>>   }

Hi, CJ.

I think my patch is correct based on the old commit: 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.19-rc2&id=09700c504d8e63faffd2a2235074e8c5d130cb8f

Bugs and fix solutions in this 09700c504d8e63-commit are very similar with mine.

Besides, I also find similar new bugs in other two files in the same directory 'powernv', 
so I have merged all three files' patches into one commit.  '[PATCH v2] powerpc: powernv: Fix refcount leak bug'.

Thanks.

Liang

Re: [PATCH] powerpc: powernv: Fix refcount leak bug in opal-powercap

[Christophe JAILLET]

Le 17/06/2022 à 07:42, Liang He a écrit :
> 
> 
> 
> At 2022-06-17 13:01:27, "Christophe JAILLET" <christophe.jaillet@wanadoo.fr> wrote:
>> Le 17/06/2022 à 06:20, Liang He a écrit :
>>> In opal_powercap_init(), of_find_compatible_node() will return
>>> a node pointer with refcount incremented. We should use of_node_put()
>>> in fail path or when it is not used anymore.
>>>
>>> Besides, for_each_child_of_node() will automatically *inc* and *dec*
>>> refcount during iteration. However, we should add the of_node_put()
>>> if there is a break.
>>
>> Hi,
>>
>> I'm not sure that your patch is right here. Because of this *inc* and
>> *dec* things, do we still need to of_node_put(powercap) once we have
>> entered for_each_child_of_node?
>>
>> I think that this reference will be released on the first iteration of
>> the loop.
>>
> 
> Hi, CJ,
> 
> Thanks for your reply and I want have a discuss.
> 
> Based on my review on the src of 'of_get_next_child',  there is only
> *inc* for next and *dec* for pre as follow.
> 
> (|node| == powercap)
> ======__of_get_next_child( |node|, prev)======
>       ...
>          next = prev? prev->sibling:|node|->child;
> 	of_node_get(next);
> 	of_node_put(prev);
>       ...
> =========================
> 
> However, there is no any code to release the |node| (i.e., *powercap*).
> 
> Am I right?   If I am wrong, please correct me, thanks.

You are right.
I mis-read __of_get_next_child(().

CJ


> 
>>
>> Maybe of_node_put(powercap) should be duplicated everywhere it is
>> relevant and removed from the error handling path?
>> Or an additional reference should be taken before the loop?
>> Or adding a new label with "powercap = NULL" and branching there when
>> needed?
>>
>> CJ
> 
> If my understanding is right, I think current patch is right.
> 
> Otherwise, I will make a new patch to handle that, Thanks.
> 
> Liang
> 
>>
>>>
>>> Signed-off-by: Liang He <windhl@126.com>
>>> ---
>>>    arch/powerpc/platforms/powernv/opal-powercap.c | 5 ++++-
>>>    1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
>>> index 64506b46e77b..b102477d3f95 100644
>>> --- a/arch/powerpc/platforms/powernv/opal-powercap.c
>>> +++ b/arch/powerpc/platforms/powernv/opal-powercap.c
>>> @@ -153,7 +153,7 @@ void __init opal_powercap_init(void)
>>>    	pcaps = kcalloc(of_get_child_count(powercap), sizeof(*pcaps),
>>>    			GFP_KERNEL);
>>>    	if (!pcaps)
>>> -		return;
>>> +		goto out_powercap;
>>>    
>>>    	powercap_kobj = kobject_create_and_add("powercap", opal_kobj);
>>>    	if (!powercap_kobj) {
>>> @@ -236,6 +236,9 @@ void __init opal_powercap_init(void)
>>>    		kfree(pcaps[i].pg.name);
>>>    	}
>>>    	kobject_put(powercap_kobj);
>>> +	of_node_put(node);
>>>    out_pcaps:
>>>    	kfree(pcaps);
>>> +out_powercap:
>>> +	of_node_put(powercap);
>>>    }