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@xxxxxxxxxxxxxx>
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
