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

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Date:   Wed, 14 Mar 2018 19:56:52 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Arvind Yadav <arvind.yadav.cs@...il.com>
Cc:     dwmw2@...radead.org, computersforpeace@...il.com,
        boris.brezillon@...e-electrons.com, marek.vasut@...il.com,
        richard@....at, 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 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.

>  	return err;
>  }



-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com