| Message ID | 20231020-strncpy-drivers-power-supply-bq256xx_charger-c-v1-1-2fad856124f9@google.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | power: supply: bq256xx: replace deprecated strncpy with strscpy | expand |
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: linux-hardening@vger.kernel.org > 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 <justinstitt@google.com> Reviewed-by: Kees Cook <keescook@chromium.org>
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,
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);
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: linux-hardening@vger.kernel.org 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 <justinstitt@google.com> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/power/supply/bq256xx_charger.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7 change-id: 20231020-strncpy-drivers-power-supply-bq256xx_charger-c-be69c58602e6 Best regards, -- Justin Stitt <justinstitt@google.com>