linux-kernel - Re: [PATCH] Input: gpio_keys_polled - use struct_size() in devm

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Message-ID: <20190623063344.GC204275@dtor-ws>
Date:   Sat, 22 Jun 2019 23:33:44 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: gpio_keys_polled - use struct_size() in
 devm_kzalloc()

On Wed, Jun 19, 2019 at 09:26:55AM -0500, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct gpio_keys_polled_dev {
> 	...
>         struct gpio_keys_button_data data[0];
> };
> 
> size = sizeof(struct gpio_keys_polled_dev) + count * sizeof(struct gpio_keys_button_data);
> instance = devm_kzalloc(dev, size, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> instance = devm_kzalloc(dev, struct_size(instance, data, count), GFP_KERNEL);
> 
> Notice that, in this case, variable size is not necessary, hence it
> is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Applied, thank you.

> ---
>  drivers/input/keyboard/gpio_keys_polled.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/keyboard/gpio_keys_polled.c b/drivers/input/keyboard/gpio_keys_polled.c
> index edc7262103b9..c4087be0c2e0 100644
> --- a/drivers/input/keyboard/gpio_keys_polled.c
> +++ b/drivers/input/keyboard/gpio_keys_polled.c
> @@ -235,7 +235,6 @@ static int gpio_keys_polled_probe(struct platform_device *pdev)
>  	struct gpio_keys_polled_dev *bdev;
>  	struct input_polled_dev *poll_dev;
>  	struct input_dev *input;
> -	size_t size;
>  	int error;
>  	int i;
>  
> @@ -250,9 +249,8 @@ static int gpio_keys_polled_probe(struct platform_device *pdev)
>  		return -EINVAL;
>  	}
>  
> -	size = sizeof(struct gpio_keys_polled_dev) +
> -			pdata->nbuttons * sizeof(struct gpio_keys_button_data);
> -	bdev = devm_kzalloc(dev, size, GFP_KERNEL);
> +	bdev = devm_kzalloc(dev, struct_size(bdev, data, pdata->nbuttons),
> +			    GFP_KERNEL);
>  	if (!bdev) {
>  		dev_err(dev, "no memory for private data\n");
>  		return -ENOMEM;
> -- 
> 2.21.0
> 

-- 
Dmitry