linux-kernel - Re: [PATCH] powerpc: kernel: fix a refcount leak in format

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Date:   Wed, 2 Mar 2022 09:34:02 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     Tyrel Datwyler <tyreld@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        benh@...nel.crashing.org, paulus@...ba.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: kernel: fix a refcount leak in format_show()

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@...il.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
>