linux-kernel - Re: [PATCH] [SCSI] iscsi_boot_sysfs: Fix a memory leak in iscsi_boot_destroy

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Date:	Wed, 11 Dec 2013 10:47:07 +0800
From:	Ethan Zhao <ethan.kernel@...il.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	michaelc@...wisc.edu, pjones@...hat.com,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [SCSI] iscsi_boot_sysfs: Fix a memory leak in iscsi_boot_destroy_kset()

On Tue, Dec 10, 2013 at 10:11 PM, Konrad Rzeszutek Wilk
<konrad.wilk@...cle.com> wrote:
> Ethan Zhao <ethan.kernel@...il.com> wrote:
>>Konrad,
>>
>> boot_kset was allocated when module loaded by
>>ibft_init()
>>  iscsi_boot_create_kset()
>>     kzalloc()
>>
>>but wasn't freed when module unloaded by
>>ibft_exit()
>>   ibft_cleanup()
>>     iscsi_boot_destroy_kset()
>>
>>Thanks,
>>Ethan
>>
>>On Tue, Dec 10, 2013 at 5:30 AM, Konrad Rzeszutek Wilk
>><konrad.wilk@...cle.com> wrote:
>>> On Mon, Dec 09, 2013 at 05:37:11PM +0800, Ethan Zhao wrote:
>>>> From: "Ethan Zhao" <ethan.kernel@...il.com>
>>>>
>>>> Load and unload iscsi_ibft module will cause kernel memory leak, fix
>>it
>>>> in scsi/iscsi_boot_sysfs.c iscsi_boot_destroy_kset().
>>>>
>>>
>>> Is there a stack trace?
>>>> Signed-off-by: Ethan Zhao <ethan.kernel@...il.com>
>>>> ---
>>>>  drivers/scsi/iscsi_boot_sysfs.c | 1 +
>>>>  1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/scsi/iscsi_boot_sysfs.c
>>b/drivers/scsi/iscsi_boot_sysfs.c
>>>> index 14c1c8f..680bf6f 100644
>>>> --- a/drivers/scsi/iscsi_boot_sysfs.c
>>>> +++ b/drivers/scsi/iscsi_boot_sysfs.c
>>>> @@ -490,5 +490,6 @@ void iscsi_boot_destroy_kset(struct
>>iscsi_boot_kset *boot_kset)
>>>>               iscsi_boot_remove_kobj(boot_kobj);
>>>>
>>>>       kset_unregister(boot_kset->kset);
>>>> +     kfree(boot_kset);
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(iscsi_boot_destroy_kset);
>>>> --
>>>> 1.8.3.4 (Apple Git-47)
>>>>
>
> Right. In the past we did not do that b/c certain drivers (like broadcom) would allocate on the kset their name and try to free (the driver would after freeing the ibft). So you would end up with this patch a double free ( and it might be fixed by now but I can't recall).
>
> My question was - did you observer a crash or bug. Hence the question about stack trace? How did you see this?

That is quite simple, just like fuzzy test, load and unload a module
millions of times with a script in low memory size machine, in the
meanwhile, monitor OOM etc.

Thanks,
Ethan

>
> Thank you.
>
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