linux-kernel - Re: [PATCH 1/3] kobject : kobject_set_name

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Date:	Thu, 14 May 2009 20:59:39 +0800
From:	Dave Young <hidave.darkstar@...il.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Greg KH <gregkh@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] kobject : kobject_set_name_vargs leak fix

On Thu, May 14, 2009 at 8:38 PM, Ming Lei <tom.leiming@...il.com> wrote:
> 2009/5/14 Dave Young <hidave.darkstar@...il.com>:
>> On Mon, May 11, 2009 at 2:16 PM, Dave Young <hidave.darkstar@...il.com> wrote:
>>> kobject_set_name_vargs will leak the old_name when return -ENOMEM,
>>> move the kfree(old_name) before the return path.
>>
>> Hi, greg
>>
>> I rethought about this problem, does such issue exist really? I means
>> that kobject->name != NULL scenario.
>>
>> there's following comments of this function:
>>
>>  * This sets the name of the kobject.  If you have already added the
>>  * kobject to the system, you must call kobject_rename() in order to
>>  * change the name of the kobject
>>
>> So what if something like :
>>
>> if (kobject->name) {
>>  WARN(1, KERN_WARNING, "there's name for kobject already!");
>>  return -EINVAL;
>> }
>>
>> if (!fmt)
>>  return 0;
>>
>>>
>>> Signed-off-by: Dave Young <hidave.darkstar@...il.com>
>>> ---
>>> lib/kobject.c |    2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff -uprN linux.old/lib/kobject.c linux.new/lib/kobject.c
>>> --- linux.old/lib/kobject.c     2009-05-11 13:59:01.000000000 +0800
>>> +++ linux.new/lib/kobject.c     2009-05-11 13:59:34.000000000 +0800
>>> @@ -221,6 +221,7 @@ int kobject_set_name_vargs(struct kobjec
>>>        if (kobj->name && !fmt)
>>>                return 0;
>>>
>>> +       kfree(old_name);
>>>        kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
>>>        if (!kobj->name)
>>>                return -ENOMEM;
>
> IMO, Greg means it is better that the fix should be :
>        if (!kobj->name) {
>                kobj->name = old_name;
>                return -ENOMEM;
>        }
>
> Right?

Hm, it's better against my original patch. I have gave up the approach.

It does not make sense for (!old_name) case , furthermore as my reply
kobject with name set before should not come into this function,
kobject_rename should be used instead.

>
>>> @@ -229,7 +230,6 @@ int kobject_set_name_vargs(struct kobjec
>>>        while ((s = strchr(kobj->name, '/')))
>>>                s[0] = '!';
>>>
>>> -       kfree(old_name);
>>>        return 0;
>>>  }
>>>
>>
>>
>>
>> --
>> Regards
>> dave
>> --
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>>
>
>
>
> --
> Lei Ming
>



-- 
Regards
dave
--
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