2023-10-20 19:11:51

by Justin Stitt

Subject: [PATCH] power: supply: bq25980: 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 bq->model_name to be NUL-terminated based on its usage with
sysfs_emit and format strings:

val->strval is assigned to bq->model_name in
bq25980_get_charger_property():
| val->strval = bq->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 bq25980_get_charger_property():
| static const struct power_supply_desc bq25980_power_supply_desc = {
...
| .get_property = bq25980_get_charger_property,

Moreover, no NUL-padding is required as bq is zero-allocated in
bq25980_charger.c:
| bq = devm_kzalloc(dev, sizeof(*bq), 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 [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]
Similar-to: https://lore.kernel.org/all/20231020-strncpy-drivers-power-supply-bq24190_charger-c-v1-1-e896223cb795@google.com/
Similar-to: https://lore.kernel.org/all/20231020-strncpy-drivers-power-supply-bq2515x_charger-c-v1-1-46664c6edf78@google.com/
Signed-off-by: Justin Stitt <[email protected]>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
drivers/power/supply/bq25980_charger.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/power/supply/bq25980_charger.c b/drivers/power/supply/bq25980_charger.c
index d8411722266f..0c5e2938bb36 100644
--- a/drivers/power/supply/bq25980_charger.c
+++ b/drivers/power/supply/bq25980_charger.c
@@ -1223,7 +1223,7 @@ static int bq25980_probe(struct i2c_client *client)

mutex_init(&bq->lock);

- strncpy(bq->model_name, id->name, I2C_NAME_SIZE);
+ strscpy(bq->model_name, id->name, sizeof(bq->model_name));
bq->chip_info = &bq25980_chip_info_tbl[id->driver_data];

bq->regmap = devm_regmap_init_i2c(client,

---
base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7
change-id: 20231020-strncpy-drivers-power-supply-bq25980_charger-c-9b8b8f11d309

Best regards,
--
Justin Stitt <[email protected]>

2023-10-21 00:54:35

by Sebastian Reichel

Subject: Re: [PATCH] power: supply: bq25980: replace deprecated strncpy with strscpy

On Fri, 20 Oct 2023 19:11:07 +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 bq->model_name to be NUL-terminated based on its usage with
> sysfs_emit and format strings:
>
> [...]

Applied, thanks!

[1/1] power: supply: bq25980: replace deprecated strncpy with strscpy
commit: afb0379b0f6657b9f626d23c3bb00b4e8823bd2d

Best regards,
--
Sebastian Reichel <[email protected]>