linux-kernel - Re: [PATCH 2/2 v2] mtd: ubi: use put_device() if device

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Date:   Thu, 15 Mar 2018 14:17:25 +0530
From:   Arvind Yadav <arvind.yadav.cs@...il.com>
To:     Richard Weinberger <richard@....at>
Cc:     dwmw2@...radead.org, computersforpeace@...il.com,
        boris.brezillon@...e-electrons.com, marek.vasut@...il.com,
        cyrille.pitchen@...ev4u.fr, dedekind1@...il.com,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org
Subject: Re: [PATCH 2/2 v2] mtd: ubi: use put_device() if device_register fail



On Thursday 15 March 2018 01:25 PM, Richard Weinberger wrote:
> Am Donnerstag, 15. März 2018, 08:20:31 CET schrieb Arvind Yadav:
>> if device_register() returned an error! Always use put_device()
>> to give up the reference initialized.
> Like DaveM said, there is no need to shout and use "!".

I will fix this and send you update patch.
>   
>> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
>> ---
>> change in v2:
>>          Fix use-after-free bug. move put_device() after cdev_del().
>>
>>   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..93c6163 100644
>> --- a/drivers/mtd/ubi/vmt.c
>> +++ b/drivers/mtd/ubi/vmt.c
>> @@ -610,6 +610,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct
>> ubi_volume *vol)
>>
>>   out_cdev:
>>   	cdev_del(&vol->cdev);
>> +	put_device(&vol->dev);
>>   	return err;
> The more I dig into device code, the more questions I have.
> Why is cdev_del() not part of the release function?
>
> Thanks,
> //richard

Yes, It's should be a part release function.

~arvind