On Tue, Jun 18, 2019 at 10:23:25AM -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_drvdata {
> ...
> struct gpio_button_data data[0];
> };
>
>
> size = sizeof(struct gpio_keys_drvdata) + count * sizeof(struct
> gpio_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 <[email protected]>
Applied, thank you.
> ---
> drivers/input/keyboard/gpio_keys.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/input/keyboard/gpio_keys.c
> b/drivers/input/keyboard/gpio_keys.c
> index 6cd199e8a370..c186c2552b04 100644
> --- a/drivers/input/keyboard/gpio_keys.c
> +++ b/drivers/input/keyboard/gpio_keys.c
> @@ -774,7 +774,6 @@ static int gpio_keys_probe(struct platform_device *pdev)
> struct fwnode_handle *child = NULL;
> struct gpio_keys_drvdata *ddata;
> struct input_dev *input;
> - size_t size;
> int i, error;
> int wakeup = 0;
>
> @@ -784,9 +783,8 @@ static int gpio_keys_probe(struct platform_device *pdev)
> return PTR_ERR(pdata);
> }
>
> - size = sizeof(struct gpio_keys_drvdata) +
> - pdata->nbuttons * sizeof(struct gpio_button_data);
> - ddata = devm_kzalloc(dev, size, GFP_KERNEL);
> + ddata = devm_kzalloc(dev, struct_size(ddata, data, pdata->nbuttons),
> + GFP_KERNEL);
> if (!ddata) {
> dev_err(dev, "failed to allocate state\n");
> return -ENOMEM;
> --
> 2.21.0
>
--
Dmitry
