linux-kernel - Re: [PATCH 2/2] mtd: ubi: use put_device() if device

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Date:   Thu, 15 Mar 2018 12:11:19 +0530
From:   Arvind Yadav <arvind.yadav.cs@...il.com>
To:     Richard Weinberger <richard@....at>,
        Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     dwmw2@...radead.org, computersforpeace@...il.com,
        boris.brezillon@...e-electrons.com, marek.vasut@...il.com,
        cyrille.pitchen@...ev4u.fr, dedekind1@...il.com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mtd: ubi: use put_device() if device_register fail



On Thursday 15 March 2018 12:55 AM, Richard Weinberger wrote:
> Am Mittwoch, 14. März 2018, 19:56:52 CET schrieb Boris Brezillon:
>> On Fri,  9 Mar 2018 16:20:49 +0530
>>
>> Arvind Yadav <arvind.yadav.cs@...il.com> wrote:
>>> if device_register() returned an error! Always use put_device()
>>> to give up the reference initialized.
>>>
>>> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
>>> ---
>>>
>>>   drivers/mtd/ubi/vmt.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
>>> index 3fd8d7f..db85b68 100644
>>> --- a/drivers/mtd/ubi/vmt.c
>>> +++ b/drivers/mtd/ubi/vmt.c
>>> @@ -609,6 +609,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct
>>> ubi_volume *vol)>
>>>   	return err;
>>>   
>>>   out_cdev:
>>> +	put_device(&vol->dev);
>>>
>>>   	cdev_del(&vol->cdev);
>> use-after-free bug here: put_device() has freed the vol obj, and you're
>> dereferencing the pointer just after that.
Thanks Boris, to point out this error.
> eeek, thanks for looking at more context.
> Arvind, while you are right that put_device() is missing, please double check
> that freeing the devices is also correct.
>
> Thanks,
> //richard
Sorry for that. I will take care of this.

~arvind