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
bq256xx_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 bq256xx_get_charger_property():
| static const struct power_supply_desc bq256xx_power_supply_desc = {
...
| .get_property = bq256xx_get_charger_property,
Moreover, no NUL-padding is required as bq is zero-allocated in
bq256xx_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/bq256xx_charger.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/power/supply/bq256xx_charger.c b/drivers/power/supply/bq256xx_charger.c
index 82d3cd5ee2f9..85e1185275b9 100644
--- a/drivers/power/supply/bq256xx_charger.c
+++ b/drivers/power/supply/bq256xx_charger.c
@@ -1706,7 +1706,7 @@ static int bq256xx_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->regmap = devm_regmap_init_i2c(client,
bq->chip_info->bq256xx_regmap_config);
---
base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7
change-id: 20231020-strncpy-drivers-power-supply-bq256xx_charger-c-be69c58602e6
Best regards,
--
Justin Stitt <[email protected]>
On Fri, Oct 20, 2023 at 07:05:25PM +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:
>
> val->strval is assigned to bq->model_name in
> bq256xx_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 bq256xx_get_charger_property():
> | static const struct power_supply_desc bq256xx_power_supply_desc = {
> ...
> | .get_property = bq256xx_get_charger_property,
>
> Moreover, no NUL-padding is required as bq is zero-allocated in
> bq256xx_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]>
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
On Fri, 20 Oct 2023 19:05:25 +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: bq256xx: replace deprecated strncpy with strscpy
commit: 056a75599f5e676d497bbf9b29157877f542e56b
Best regards,
--
Sebastian Reichel <[email protected]>