On Fri, Oct 20, 2023 at 06:14:47PM +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 bdi->model_name to be NUL-terminated based on its usage with
> sysfs_emit and format strings:
>
> val->strval is assigned to bdi->model_name in
> bq24190_charger_get_property():
> 1186 | val->strval = bdi->model_name;
>
> ... then in power_supply_sysfs.c we use value.strval with a format string:
> 311 | ret = sysfs_emit(buf, "%s\n", value.strval);
>
> we assigned value.strval via:
> 285 | ret = power_supply_get_property(psy, psp, &value);
> ... which invokes psy->desc->get_property():
> 1210 | return psy->desc->get_property(psy, psp, val);
>
> with bq24190_charger_get_property():
> 1320 | static const struct power_supply_desc bq24190_charger_desc = {
> ...
> 1325 | .get_property = bq24190_charger_get_property,
>
> Moreover, no NUL-padding is required as bdi is zero-allocated in
> bq24190_charger.c:
> 1798 | bdi = devm_kzalloc(dev, sizeof(*bdi), GFP_KERNEL);
>
> Considering the above, 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: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinst...@google.com>
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/power/supply/bq24190_charger.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/power/supply/bq24190_charger.c
> b/drivers/power/supply/bq24190_charger.c
> index 3f99cb9590ba..1db290ee2591 100644
> --- a/drivers/power/supply/bq24190_charger.c
> +++ b/drivers/power/supply/bq24190_charger.c
> @@ -1803,7 +1803,7 @@ static int bq24190_probe(struct i2c_client *client)
>
> bdi->client = client;
> bdi->dev = dev;
> - strncpy(bdi->model_name, id->name, I2C_NAME_SIZE);
> + strscpy(bdi->model_name, id->name, sizeof(bdi->model_name));
struct bq24190_dev_info {
...
char model_name[I2C_NAME_SIZE];
Length replacement looks correct.
struct i2c_device_id {
char name[I2C_NAME_SIZE];
And it looks like this wasn't accidentally leaving strings unterminated,
so that's nice.
Reviewed-by: Kees Cook <keesc...@chromium.org>
--
Kees Cook
