On 10/20/23 21:39, 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 bat->name to be NUL-terminated based on its usage with
strcmp():
power_supply_core.c:
445: return strcmp(psy->desc->name, name) == 0;
... and also by the manual `... - 1` for the length argument of the
original strncpy() invocation.
Furthermore, no NUL-padding is needed as bat is zero-allocated before
calling spwr_battery_init():
826: bat = devm_kzalloc(&sdev->dev, sizeof(*bat), GFP_KERNEL);
827: if (!bat)
828: return -ENOMEM;
829:
830: spwr_battery_init(bat, sdev, p->registry, p->name);
... this means any further NUL-byte assignments (like the ones that
strncpy() does) are redundant.
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)).
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@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
Thanks!
Reviewed-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
Tested-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
---
Changes in v2:
- fix subject line
- Link to v1: https://lore.kernel.org/r/20231020-strncpy-drivers-power-supply-surface_battery-c-v1-1-cabaea50e667@xxxxxxxxxx
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
drivers/power/supply/surface_battery.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/power/supply/surface_battery.c b/drivers/power/supply/surface_battery.c
index 19d2f8834e56..196d290dc596 100644
--- a/drivers/power/supply/surface_battery.c
+++ b/drivers/power/supply/surface_battery.c
@@ -722,7 +722,7 @@ static void spwr_battery_init(struct spwr_battery_device *bat, struct ssam_devic
struct ssam_event_registry registry, const char *name)
{
mutex_init(&bat->lock);
- strncpy(bat->name, name, ARRAY_SIZE(bat->name) - 1);
+ strscpy(bat->name, name, sizeof(bat->name));
bat->sdev = sdev;
---
base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7
change-id: 20231020-strncpy-drivers-power-supply-surface_battery-c-b0c84b05ac28
Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>
