[PATCH] powerpc: kernel: fix a refcount leak in format_show()

[PATCH] powerpc: kernel: fix a refcount leak in format_show()

[Hangyu Hua]

node needs to be dropped when of_property_read_string fails. So an earlier call
to of_node_put is required here.

Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
---
 arch/powerpc/kernel/secvar-sysfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
index a0a78aba2083..cd0fa7028d86 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -30,13 +30,12 @@ static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
 		return -ENODEV;
 
 	rc = of_property_read_string(node, "format", &format);
+	of_node_put(node);
 	if (rc)
 		return rc;
 
 	rc = sprintf(buf, "%s\n", format);
 
-	of_node_put(node);
-
 	return rc;
 }
 
-- 
2.25.1

Re: [PATCH] powerpc: kernel: fix a refcount leak in format_show()

[Michael Ellerman]

Hangyu Hua <hbh25y@gmail.com> writes:
> node needs to be dropped when of_property_read_string fails. So an earlier call
> to of_node_put is required here.

That's true but ...

> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
> index a0a78aba2083..cd0fa7028d86 100644
> --- a/arch/powerpc/kernel/secvar-sysfs.c
> +++ b/arch/powerpc/kernel/secvar-sysfs.c
> @@ -30,13 +30,12 @@ static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
>  		return -ENODEV;

There's also a reference leak there ^

So if you're going to touch this code I'd like you to fix both reference
leaks in a single patch please.

Having the error cases set rc and then goto "out" which does the
of_node_put() is the obvious solution I think.

cheers

>  	rc = of_property_read_string(node, "format", &format);
> +	of_node_put(node);
>  	if (rc)
>  		return rc;
>  
>  	rc = sprintf(buf, "%s\n", format);
>  
> -	of_node_put(node);
> -
>  	return rc;
>  }
>  
> -- 
> 2.25.1

Re: [PATCH] powerpc: kernel: fix a refcount leak in format_show()

[Tyrel Datwyler]

On 3/1/22 04:55, Michael Ellerman wrote:
> Hangyu Hua <hbh25y@gmail.com> writes:
>> node needs to be dropped when of_property_read_string fails. So an earlier call
>> to of_node_put is required here.
> 
> That's true but ...
> 
>> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
>> index a0a78aba2083..cd0fa7028d86 100644
>> --- a/arch/powerpc/kernel/secvar-sysfs.c
>> +++ b/arch/powerpc/kernel/secvar-sysfs.c
>> @@ -30,13 +30,12 @@ static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
>>  		return -ENODEV;
> 
> There's also a reference leak there ^
> 
> So if you're going to touch this code I'd like you to fix both reference
> leaks in a single patch please.
> 
> Having the error cases set rc and then goto "out" which does the
> of_node_put() is the obvious solution I think.

update_kobj_size() in the same source file provides a good example of the
suggested solution.

-Tyrel

> 
> cheers
> 
>>  	rc = of_property_read_string(node, "format", &format);
>> +	of_node_put(node);
>>  	if (rc)
>>  		return rc;
>>  
>>  	rc = sprintf(buf, "%s\n", format);
>>  
>> -	of_node_put(node);
>> -
>>  	return rc;
>>  }
>>  
>> -- 
>> 2.25.1

Re: [PATCH] powerpc: kernel: fix a refcount leak in format_show()

[Hangyu Hua]

Thanks. I will resubmit my patch latter.

On 2022/3/2 03:50, Tyrel Datwyler wrote:
> On 3/1/22 04:55, Michael Ellerman wrote:
>> Hangyu Hua <hbh25y@gmail.com> writes:
>>> node needs to be dropped when of_property_read_string fails. So an earlier call
>>> to of_node_put is required here.
>>
>> That's true but ...
>>
>>> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
>>> index a0a78aba2083..cd0fa7028d86 100644
>>> --- a/arch/powerpc/kernel/secvar-sysfs.c
>>> +++ b/arch/powerpc/kernel/secvar-sysfs.c
>>> @@ -30,13 +30,12 @@ static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
>>>   		return -ENODEV;
>>
>> There's also a reference leak there ^
>>
>> So if you're going to touch this code I'd like you to fix both reference
>> leaks in a single patch please.
>>
>> Having the error cases set rc and then goto "out" which does the
>> of_node_put() is the obvious solution I think.
> 
> update_kobj_size() in the same source file provides a good example of the
> suggested solution.
> 
> -Tyrel
> 
>>
>> cheers
>>
>>>   	rc = of_property_read_string(node, "format", &format);
>>> +	of_node_put(node);
>>>   	if (rc)
>>>   		return rc;
>>>   
>>>   	rc = sprintf(buf, "%s\n", format);
>>>   
>>> -	of_node_put(node);
>>> -
>>>   	return rc;
>>>   }
>>>   
>>> -- 
>>> 2.25.1
>