[PATCH v4] hwmon: (acpi_power_meter) replace open-coded kmemdup_nul

[Justin Stitt]

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

Let's refactor this kcalloc() + strncpy() into a kmemdup_nul() which has
more obvious behavior and is less error prone.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
---
Changes in v4:
- drop +1 from length arg (thanks Kees)
- reword subject line (thanks Kees)
- rebase onto 6465e260f4879080
- Link to v3: https://lore.kernel.org/r/20230921-strncpy-drivers-hwmon-acpi_power_meter-c-v3-1-307552c6ec3f@xxxxxxxxxx

Changes in v3:
- refactor to use kmemdup_nul() (thanks Thomas and Kees)
- change commit msg to reflect ^
- rebase onto 2cf0f71562387282
- Link to v2: https://lore.kernel.org/r/20230919-strncpy-drivers-hwmon-acpi_power_meter-c-v2-1-8348432d6442@xxxxxxxxxx

Changes in v2:
- use memcpy over strscpy (thanks Kees)
- Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-hwmon-acpi_power_meter-c-v1-1-905297479fe8@xxxxxxxxxx
---
 drivers/hwmon/acpi_power_meter.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
index fa28d447f0df..c13b5c8a0433 100644
--- a/drivers/hwmon/acpi_power_meter.c
+++ b/drivers/hwmon/acpi_power_meter.c
@@ -796,14 +796,13 @@ static int read_capabilities(struct acpi_power_meter_resource *resource)
 			goto error;
 		}
 
-		*str = kcalloc(element->string.length + 1, sizeof(u8),
-			       GFP_KERNEL);
+		*str = kmemdup_nul(element->string.pointer, element->string.length,
+						 GFP_KERNEL);
 		if (!*str) {
 			res = -ENOMEM;
 			goto error;
 		}
 
-		strncpy(*str, element->string.pointer, element->string.length);
 		str++;
 	}
 

---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230914-strncpy-drivers-hwmon-acpi_power_meter-c-c9f2d8053bef

Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>