Re: [PATCH v3] gpio: cdev: check if uAPI v2 config attributes are correctly zeroed

[Kent Gibson]

On Thu, May 21, 2026 at 10:42:16AM +0200, Bartosz Golaszewski wrote:
> We check the padding of other uAPI v2 structures but not that of line
> config attributes. For used attributes: check if their padding is
> zeroed, for unused: check if the entire structure is zeroed.
> 
> Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>

Reviewed-by: Kent Gibson <warthog618@xxxxxxxxx>

> ---
> Changes in v3:
> - Don't try to check unused attributes if there are none
> - Don't reuse the loop iterator from the attribute padding check
> - Link to v2: https://patch.msgid.link/20260520-gpio-cdev-attr-padding-check-v2-1-0010daf8059f@xxxxxxxxxxxxxxxx
> 
> Changes in v2:
> - Make checking even stricter: check if padding is zeroed for used
>   attributes, for unused ones: check if the entire struct is zeroed
> - Link to v1: https://patch.msgid.link/20260519-gpio-cdev-attr-padding-check-v1-1-a0c6d4a698bf@xxxxxxxxxxxxxxxx
> ---
>  drivers/gpio/gpiolib-cdev.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index f36b7c06996d70b2286edbd181899e4c572b9086..82f27db0b2304679eae4c4f28302e9845d7cbaa3 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -1184,6 +1184,7 @@ static int gpio_v2_line_flags_validate(u64 flags)
>  static int gpio_v2_line_config_validate(struct gpio_v2_line_config *lc,
>  					unsigned int num_lines)
>  {
> +	size_t unused_attrs;
>  	unsigned int i;
>  	u64 flags;
>  	int ret;
> @@ -1191,9 +1192,21 @@ static int gpio_v2_line_config_validate(struct gpio_v2_line_config *lc,
>  	if (lc->num_attrs > GPIO_V2_LINE_NUM_ATTRS_MAX)
>  		return -EINVAL;
>  
> +	unused_attrs = GPIO_V2_LINE_NUM_ATTRS_MAX - lc->num_attrs;
> +
>  	if (!mem_is_zero(lc->padding, sizeof(lc->padding)))
>  		return -EINVAL;
>  
> +	for (i = 0; i < lc->num_attrs; i++) {
> +		if (lc->attrs[i].attr.padding != 0)
> +			return -EINVAL;
> +	}
> +
> +	if (unused_attrs) {
> +		if (!mem_is_zero(&lc->attrs[lc->num_attrs], unused_attrs * sizeof(*lc->attrs)))
> +			return -EINVAL;
> +	}
> +
>  	for (i = 0; i < num_lines; i++) {
>  		flags = gpio_v2_line_config_flags(lc, i);
>  		ret = gpio_v2_line_flags_validate(flags);
> 
> ---
> base-commit: 6a50ba100ace43f43c87384367eb2d2605fcc16c
> change-id: 20260519-gpio-cdev-attr-padding-check-7e52c98a3de7
> 
> Best regards,
> -- 
> Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
>