2023-09-19 08:56:09

by Justin Stitt

Subject: [PATCH v2] hwmon: refactor deprecated strncpy

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

A trailing zero is already handled by the kcalloc
| *str = kcalloc(element->string.length + 1, sizeof(u8), GFP_KERNEL);
... which makes memcpy() a suitable replacement to strncpy.

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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
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@google.com
---
drivers/hwmon/acpi_power_meter.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
index fa28d447f0df..82e99aec4a33 100644
--- a/drivers/hwmon/acpi_power_meter.c
+++ b/drivers/hwmon/acpi_power_meter.c
@@ -803,7 +803,7 @@ static int read_capabilities(struct acpi_power_meter_resource *resource)
goto error;
}

- strncpy(*str, element->string.pointer, element->string.length);
+ memcpy(*str, element->string.pointer, element->string.length);
str++;
}


---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230914-strncpy-drivers-hwmon-acpi_power_meter-c-c9f2d8053bef

Best regards,
--
Justin Stitt <[email protected]>

2023-09-19 09:15:21

by Thomas Weißschuh

Subject: Re: [PATCH v2] hwmon: refactor deprecated strncpy

On 2023-09-19 05:07:55+0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>
> A trailing zero is already handled by the kcalloc
> | *str = kcalloc(element->string.length + 1, sizeof(u8), GFP_KERNEL);
> ... which makes memcpy() a suitable replacement to strncpy.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> 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@google.com
> ---
> drivers/hwmon/acpi_power_meter.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
> index fa28d447f0df..82e99aec4a33 100644
> --- a/drivers/hwmon/acpi_power_meter.c
> +++ b/drivers/hwmon/acpi_power_meter.c
> @@ -803,7 +803,7 @@ static int read_capabilities(struct acpi_power_meter_resource *resource)
> goto error;
> }
>
> - strncpy(*str, element->string.pointer, element->string.length);
> + memcpy(*str, element->string.pointer, element->string.length);

Isn't this now essentially the same as kmemdup_nul()?

> str++;
> }
>
>
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-hwmon-acpi_power_meter-c-c9f2d8053bef
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>

2023-09-20 21:05:35

by Kees Cook

Subject: Re: [PATCH v2] hwmon: refactor deprecated strncpy

On Tue, Sep 19, 2023 at 09:02:49AM +0200, Thomas Wei?schuh wrote:
> On 2023-09-19 05:07:55+0000, Justin Stitt wrote:
> > `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> >
> > A trailing zero is already handled by the kcalloc
> > | *str = kcalloc(element->string.length + 1, sizeof(u8), GFP_KERNEL);
> > ... which makes memcpy() a suitable replacement to strncpy.
> >
> > 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: [email protected]
> > Signed-off-by: Justin Stitt <[email protected]>
> > ---
> > 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@google.com
> > ---
> > drivers/hwmon/acpi_power_meter.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
> > index fa28d447f0df..82e99aec4a33 100644
> > --- a/drivers/hwmon/acpi_power_meter.c
> > +++ b/drivers/hwmon/acpi_power_meter.c
> > @@ -803,7 +803,7 @@ static int read_capabilities(struct acpi_power_meter_resource *resource)
> > goto error;
> > }
> >
> > - strncpy(*str, element->string.pointer, element->string.length);
> > + memcpy(*str, element->string.pointer, element->string.length);
>
> Isn't this now essentially the same as kmemdup_nul()?

Ah, yeah, good catch. I should add a note that the reverse of strtomem()
is kmemdup_nul() :)

Justin, can you refactor this to use kmemdup_nul() instead?

-Kees

--
Kees Cook