linux-kernel - Re: [PATCH] kobject: kzfree object in

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Message-ID: <84144f020904130937w4443ed2fjc5645824fd1377f@mail.gmail.com>
Date:	Mon, 13 Apr 2009 19:37:47 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Greg KH <greg@...ah.com>
Cc:	tom.leiming@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kobject: kzfree object in _release function

Hi Greg,

On Mon, Apr 13, 2009 at 7:31 PM, Greg KH <greg@...ah.com> wrote:
> On Sun, Apr 12, 2009 at 12:16:26AM +0800, tom.leiming@...il.com wrote:
>> From: Ming Lei <tom.leiming@...il.com>
>>
>> It helps to troubleshoot the __buggy__ case, in which
>> unreferenced objects are still accessed, using kzfree
>> to free objects safely in _release function.
>>
>> Signed-off-by: Ming Lei <tom.leiming@...il.com>
>> ---
>>  lib/kobject.c |    4 ++--
>>  1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/kobject.c b/lib/kobject.c
>> index a6dec32..cb5a562 100644
>> --- a/lib/kobject.c
>> +++ b/lib/kobject.c
>> @@ -597,7 +597,7 @@ void kobject_put(struct kobject *kobj)
>>  static void dynamic_kobj_release(struct kobject *kobj)
>>  {
>>       pr_debug("kobject: (%p): %s\n", kobj, __func__);
>> -     kfree(kobj);
>> +     kzfree(kobj);
>>  }
>>
>>  static struct kobj_type dynamic_kobj_ktype = {
>> @@ -762,7 +762,7 @@ static void kset_release(struct kobject *kobj)
>>       struct kset *kset = container_of(kobj, struct kset, kobj);
>>       pr_debug("kobject: '%s' (%p): %s\n",
>>                kobject_name(kobj), kobj, __func__);
>> -     kfree(kset);
>> +     kzfree(kset);
>
>
> What about slab-poisoning?  Shouldn't we just rely on that instead?

Yes, you should. kzfree() strictly for cases where _correctness_ of
the program requires it (i.e. security concerns).
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