linux-kernel - Re: [PATCH] kobject: Fix kobject_set_name

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Date:	Fri, 12 Mar 2010 05:46:30 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Greg KH <greg@...ah.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kobject: Fix kobject_set_name_vargs()

On Fri, Mar 12, 2010 at 05:39, Kay Sievers <kay.sievers@...y.org> wrote:
> On Fri, Mar 12, 2010 at 05:15, Greg KH <greg@...ah.com> wrote:
>> On Thu, Mar 11, 2010 at 09:50:52PM +0100, Eric Dumazet wrote:
>>> In case of kvasprintf() failure, we can leak old kobject name.
>>>
>>> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
>>> ---
>>> diff --git a/lib/kobject.c b/lib/kobject.c
>>> index 8115eb1..1247c57 100644
>>> --- a/lib/kobject.c
>>> +++ b/lib/kobject.c
>>> @@ -222,8 +222,10 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
>>>               return 0;
>>>
>>>       kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
>>> -     if (!kobj->name)
>>> +     if (!kobj->name) {
>>> +             kobj->name = old_name;
>>>               return -ENOMEM;
>>> +     }
>>
>> Are you sure?  I think we've been over this very thing many times in the
>> past...
>>
>> Kay, I can't recall the issue here, can you?
>
> I think we just lost attention to it, and never made a final decision.
> There have been some issues, I also don't really remember.
>
> I myself have an unsubmitted patch for this problem here since 9 months:
>  http://git.kernel.org/?p=linux/kernel/git/kay/patches.git;a=blob;f=kobj-leak.patch;hb=HEAD
>
> Seems, we should start thinking about the problem again. And if we
> decide to do nothing at least add a comment why we don't. :)

Found the old discussion, which ended in no action:
  http://lkml.org/lkml/2009/6/27/160

It was about simplifying the logic and not to allow to set a kobject
name several times in a row.

Sounds good to me to try that, and raise a BUG if the name is set a
second time. If we don't support that, all can be simplified, and the
original issue, that has come up again now, will be gone with that.

Thanks,
Kay
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