On Thu, Oct 12, 2023 at 09:43:02PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> We expect new_bus->id to be NUL-terminated but not NUL-padded based on
> its prior assignment through snprintf:
> | snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
>
> Due to this, a suitable replacement is `strscpy` [2] due to the fact
> that it guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding.
>
> Link:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
> [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/net/mdio/mdio-gpio.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/mdio/mdio-gpio.c b/drivers/net/mdio/mdio-gpio.c
> index 0fb3c2de0845..a1718d646504 100644
> --- a/drivers/net/mdio/mdio-gpio.c
> +++ b/drivers/net/mdio/mdio-gpio.c
> @@ -125,7 +125,7 @@ static struct mii_bus *mdio_gpio_bus_init(struct device
> *dev,
> if (bus_id != -1)
> snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
> else
> - strncpy(new_bus->id, "gpio", MII_BUS_ID_SIZE);
> + strscpy(new_bus->id, "gpio", sizeof(new_bus->id));
struct mii_bus {
...
char id[MII_BUS_ID_SIZE];
Yup, looks good. (I wonder about changing to sizeof() in the snprintf()
above it, but for a strscpy() refactor, I think this is fine.)
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
