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

[Bartosz Golaszewski]

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>
---
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>