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Date:   Fri, 20 Oct 2023 18:14:47 +0000
Mime-Version: 1.0
Message-ID: <20231020-strncpy-drivers-power-supply-bq24190_charger-c-v1-1-e896223cb795@google.com>
Subject: [PATCH] power: supply: bq24190_charger: replace deprecated strncpy
 with strscpy
From:   Justin Stitt <justinstitt@google.com>
To:     Sebastian Reichel <sre@kernel.org>
Cc:     linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
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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 <justinstitt@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));
 	mutex_init(&bdi->f_reg_lock);
 	bdi->charge_type = POWER_SUPPLY_CHARGE_TYPE_FAST;
 	bdi->f_reg = 0;

---
base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7
change-id: 20231020-strncpy-drivers-power-supply-bq24190_charger-c-6bcc105fc23b

Best regards,
--
Justin Stitt <justinstitt@google.com>