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

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Message-ID: <5296799.FRhcbj8Hd9@blindfold>
Date:   Thu, 15 Mar 2018 08:55:09 +0100
From:   Richard Weinberger <richard@....at>
To:     Arvind Yadav <arvind.yadav.cs@...il.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-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org
Subject: Re: [PATCH 2/2 v2] mtd: ubi: use put_device() if device_register fail

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 "!".
 
> 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