| Message ID | 20231020-strncpy-drivers-power-supply-surface_battery-c-v1-1-cabaea50e667@google.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | platform/surface: aggregator: replace deprecated strncpy with strscpy | expand |
Fixed the subject line in [v2]. On Fri, Oct 20, 2023 at 12:35 PM Justin Stitt <justinstitt@google.com> 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@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> > --- > 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@google.com> > [v2]: https://lore.kernel.org/r/20231020-strncpy-drivers-power-supply-surface_battery-c-v2-1-29ed16b2caf1@google.com Thanks Justin
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;
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@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/power/supply/surface_battery.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7 change-id: 20231020-strncpy-drivers-power-supply-surface_battery-c-b0c84b05ac28 Best regards, -- Justin Stitt <justinstitt@google.com>