gpio: 74x164: Annotate buffer with __counted_by()

Add the __counted_by() compiler attribute to the flexible array member
volumes to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Use struct_size() instead of manually calculating the number of bytes to
allocate the private structure with a buffer.

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250207151825.2122419-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/gpio-74x164.c b/drivers/gpio/gpio-74x164.c
index 70c662bbca7b41c7f110cafe8ff8b509cc5ad0ec..7844f8a5883471ac181352e5ad1ef25fbaa76b41 100644 (file)
--- a/drivers/gpio/gpio-74x164.c
+++ b/drivers/gpio/gpio-74x164.c
@@ -30,7 +30,7 @@ struct gen_74x164_chip {
         * register at the end of the transfer. So, to have a logical
         * numbering, store the bytes in reverse order.
         */
-       u8                      buffer[];
+       u8                      buffer[] __counted_by(registers);
 };
 
 static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
@@ -97,6 +97,7 @@ static int gen_74x164_direction_output(struct gpio_chip *gc,
 
 static int gen_74x164_probe(struct spi_device *spi)
 {
+       struct device *dev = &spi->dev;
        struct gen_74x164_chip *chip;
        u32 nregs;
        int ret;
@@ -116,10 +117,12 @@ static int gen_74x164_probe(struct spi_device *spi)
                return -EINVAL;
        }
 
-       chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL);
+       chip = devm_kzalloc(dev, struct_size(chip, buffer, nregs), GFP_KERNEL);
        if (!chip)
                return -ENOMEM;
 
+       chip->registers = nregs;
+
        chip->gpiod_oe = devm_gpiod_get_optional(&spi->dev, "enable",
                                                 GPIOD_OUT_LOW);
        if (IS_ERR(chip->gpiod_oe))
@@ -133,10 +136,7 @@ static int gen_74x164_probe(struct spi_device *spi)
        chip->gpio_chip.set = gen_74x164_set_value;
        chip->gpio_chip.set_multiple = gen_74x164_set_multiple;
        chip->gpio_chip.base = -1;
-
-       chip->registers = nregs;
        chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
-
        chip->gpio_chip.can_sleep = true;
        chip->gpio_chip.parent = &spi->dev;
        chip->gpio_chip.owner = THIS_MODULE;