power: supply: bq2515x: replace deprecated strncpy with strscpy

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 bq2515x->model_name to be NUL-terminated based on its usage with
sysfs_emit and format strings:

val->strval is assigned to bq2515x->model_name in
bq2515x_mains_get_property():
|       val->strval = bq2515x->model_name;

... then in power_supply_sysfs.c we use value.strval with a format string:
|       ret = sysfs_emit(buf, "%s\n", value.strval);

we assigned value.strval via:
|       ret = power_supply_get_property(psy, psp, &value);
... which invokes psy->desc->get_property():
|       return psy->desc->get_property(psy, psp, val);

with bq2515x_mains_get_property():
|       static const struct power_supply_desc bq2515x_mains_desc = {
...
|       	.get_property		= bq2515x_mains_get_property,

Moreover, no NUL-padding is required as bq2515x is zero-allocated in
bq2515x_charger.c:
|       bq2515x = devm_kzalloc(dev, sizeof(*bq2515x), 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.

Let's also opt to use the more idiomatic strscpy() usage of (dest, src,
sizeof(dest)) as this more closely ties the destination buffer and the
length.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Similar-to: https://lore.kernel.org/all/20231020-strncpy-drivers-power-supply-bq24190_charger-c-v1-1-e896223cb795@google.com/
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231020-strncpy-drivers-power-supply-bq2515x_charger-c-v1-1-46664c6edf78@google.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

diff --git a/drivers/power/supply/bq2515x_charger.c b/drivers/power/supply/bq2515x_charger.c
index 49fa6386a5090bb9ba0ed5cc3e42d2317aca064f..a3424f67f2b1d7b607903806291896eb68aba707 100644 (file)
--- a/drivers/power/supply/bq2515x_charger.c
+++ b/drivers/power/supply/bq2515x_charger.c
@@ -1089,7 +1089,7 @@ static int bq2515x_probe(struct i2c_client *client)
 
        bq2515x->dev = dev;
 
-       strncpy(bq2515x->model_name, id->name, I2C_NAME_SIZE);
+       strscpy(bq2515x->model_name, id->name, sizeof(bq2515x->model_name));
 
        bq2515x->info = i2c_get_match_data(client);
        bq2515x->regmap = devm_regmap_init_i2c(client,