linux-kernel - Re: [PATCH 01/12] Input: ad7897 - use managed devm_device_add

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Date:   Fri, 29 Sep 2017 16:32:12 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andi Shyti <andi@...zian.org>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andi Shyti <andi.shyti@...sung.com>,
        Michael Hennerich <michael.hennerich@...log.com>
Subject: Re: [PATCH 01/12] Input: ad7897 - use managed devm_device_add_group

Hi Andi,

On Sat, Sep 30, 2017 at 05:38:28AM +0900, Andi Shyti wrote:
> Commit 57b8ff070f98 ("driver core: add devm_device_add_group()
> and friends") has added the the managed version for creating
> sysfs group files.
> 
> Use devm_device_add_group instead of sysfs_create_group and
> remove the relative sysfs_remove_group and goto label.
> 
> CC: Michael Hennerich <michael.hennerich@...log.com>
> Signed-off-by: Andi Shyti <andi@...zian.org>
> ---
>  drivers/input/touchscreen/ad7877.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/ad7877.c b/drivers/input/touchscreen/ad7877.c
> index 9c250ae780d9..677ba38b4d1c 100644
> --- a/drivers/input/touchscreen/ad7877.c
> +++ b/drivers/input/touchscreen/ad7877.c
> @@ -783,18 +783,16 @@ static int ad7877_probe(struct spi_device *spi)
>  		goto err_free_mem;
>  	}
>  
> -	err = sysfs_create_group(&spi->dev.kobj, &ad7877_attr_group);
> +	err = devm_device_add_group(&spi->dev, &ad7877_attr_group);

This changes order of operations and ultimately may cause use-after-free
as memory for ad7877 structure will be freed before we remove
attributes.

>  	if (err)
>  		goto err_free_irq;
>  
>  	err = input_register_device(input_dev);
>  	if (err)
> -		goto err_remove_attr_group;
> +		goto err_free_irq;
>  
>  	return 0;
>  
> -err_remove_attr_group:
> -	sysfs_remove_group(&spi->dev.kobj, &ad7877_attr_group);
>  err_free_irq:
>  	free_irq(spi->irq, ts);
>  err_free_mem:
> @@ -807,8 +805,6 @@ static int ad7877_remove(struct spi_device *spi)
>  {
>  	struct ad7877 *ts = spi_get_drvdata(spi);
>  
> -	sysfs_remove_group(&spi->dev.kobj, &ad7877_attr_group);
> -
>  	ad7877_disable(ts);
>  	free_irq(ts->spi->irq, ts);
>  
> -- 
> 2.14.2
> 

Thanks.

-- 
Dmitry