[PATCH] hwmon: (pmbus/core) Replace deprecated strncpy() with strscpy()

[PATCH] hwmon: (pmbus/core) Replace deprecated strncpy() with strscpy()

[Thorsten Blum]

strncpy() is deprecated for NUL-terminated destination buffers; use
strscpy() instead.

Compile-tested only.

Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/hwmon/pmbus/pmbus_core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 787683e83db6..cdde8b03a6e9 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -1470,8 +1470,7 @@ static int pmbus_add_label(struct pmbus_data *data,
 	snprintf(label->name, sizeof(label->name), "%s%d_label", name, seq);
 	if (!index) {
 		if (phase == 0xff)
-			strncpy(label->label, lstring,
-				sizeof(label->label) - 1);
+			strscpy(label->label, lstring);
 		else
 			snprintf(label->label, sizeof(label->label), "%s.%d",
 				 lstring, phase);
-- 
2.48.1

Re: [PATCH] hwmon: (pmbus/core) Replace deprecated strncpy() with strscpy()

[Guenter Roeck]

On 2/27/25 09:39, Thorsten Blum wrote:
> strncpy() is deprecated for NUL-terminated destination buffers; use
> strscpy() instead.
> 
> Compile-tested only.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>   drivers/hwmon/pmbus/pmbus_core.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 787683e83db6..cdde8b03a6e9 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -1470,8 +1470,7 @@ static int pmbus_add_label(struct pmbus_data *data,
>   	snprintf(label->name, sizeof(label->name), "%s%d_label", name, seq);
>   	if (!index) {
>   		if (phase == 0xff)
> -			strncpy(label->label, lstring,
> -				sizeof(label->label) - 1);
> +			strscpy(label->label, lstring);

What guarantees that strlen(lstring) < sizeof(label->label) ?

Guenter

>   		else
>   			snprintf(label->label, sizeof(label->label), "%s.%d",
>   				 lstring, phase);

Re: [PATCH] hwmon: (pmbus/core) Replace deprecated strncpy() with strscpy()

[Thorsten Blum]

On 27. Feb 2025, at 23:37, Guenter Roeck wrote:
> On 2/27/25 09:39, Thorsten Blum wrote:
>> strncpy() is deprecated for NUL-terminated destination buffers; use
>> strscpy() instead.
>> Compile-tested only.
>> Link: https://github.com/KSPP/linux/issues/90
>> Cc: linux-hardening@vger.kernel.org
>> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
>> ---
> 
> What guarantees that strlen(lstring) < sizeof(label->label) ?

Hi Guenter, I don't think it matters for this patch.

If lstring >= label, strscpy() behaves the same as strncpy() because the
size argument is now one byte larger.

If lstring < label, strscpy() NUL-terminates the destination buffer, but
doesn't add NUL-padding compared to strncpy(). However, this doesn't
matter because label is already zero-initialized.

Thanks,
Thorsten

Re: [PATCH] hwmon: (pmbus/core) Replace deprecated strncpy() with strscpy()

[Guenter Roeck]

On Thu, Feb 27, 2025 at 06:39:33PM +0100, Thorsten Blum wrote:
> strncpy() is deprecated for NUL-terminated destination buffers; use
> strscpy() instead.
> 
> Compile-tested only.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>

Applied.

> ---
>  drivers/hwmon/pmbus/pmbus_core.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 787683e83db6..cdde8b03a6e9 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -1470,8 +1470,7 @@ static int pmbus_add_label(struct pmbus_data *data,
>  	snprintf(label->name, sizeof(label->name), "%s%d_label", name, seq);
>  	if (!index) {
>  		if (phase == 0xff)
> -			strncpy(label->label, lstring,
> -				sizeof(label->label) - 1);
> +			strscpy(label->label, lstring);

I added a note explaining that strscpy() uses sizeof(label->label) if the
length of the destination buffer is not provided.

Guenter