[PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Vivek BalachandharTN]

strncpy() does not guarantee NUL-termination and is deprecated for
NUL-terminated strings. Replace it with strscpy_pad(), which guarantees
NUL-termination and zero-pads the remaining bytes, matching the fixed-size
firmware tag semantics.

Signed-off-by: Vivek BalachandharTN <vivek.balachandhar@gmail.com>
---
 .../greybus/Documentation/firmware/firmware.c        | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/greybus/Documentation/firmware/firmware.c b/drivers/staging/greybus/Documentation/firmware/firmware.c
index 3b35ef6d4adb..deac8584841b 100644
--- a/drivers/staging/greybus/Documentation/firmware/firmware.c
+++ b/drivers/staging/greybus/Documentation/firmware/firmware.c
@@ -63,8 +63,8 @@ static int update_intf_firmware(int fd)
 	intf_load.major = 0;
 	intf_load.minor = 0;
 
-	strncpy((char *)&intf_load.firmware_tag, firmware_tag,
-		GB_FIRMWARE_U_TAG_MAX_SIZE);
+	strscpy_pad((char *)&intf_load.firmware_tag, firmware_tag,
+		    GB_FIRMWARE_U_TAG_MAX_SIZE);
 
 	ret = ioctl(fd, FW_MGMT_IOC_INTF_LOAD_AND_VALIDATE, &intf_load);
 	if (ret < 0) {
@@ -101,8 +101,8 @@ static int update_backend_firmware(int fd)
 	/* Get Backend Firmware Version */
 	printf("Getting Backend Firmware Version\n");
 
-	strncpy((char *)&backend_fw_info.firmware_tag, firmware_tag,
-		GB_FIRMWARE_U_TAG_MAX_SIZE);
+	strscpy_pad((char *)&backend_fw_info.firmware_tag, firmware_tag,
+		    GB_FIRMWARE_U_TAG_MAX_SIZE);
 
 retry_fw_version:
 	ret = ioctl(fd, FW_MGMT_IOC_GET_BACKEND_FW, &backend_fw_info);
@@ -129,8 +129,8 @@ static int update_backend_firmware(int fd)
 	/* Try Backend Firmware Update over Unipro */
 	printf("Updating Backend Firmware\n");
 
-	strncpy((char *)&backend_update.firmware_tag, firmware_tag,
-		GB_FIRMWARE_U_TAG_MAX_SIZE);
+	strscpy_pad((char *)&backend_update.firmware_tag, firmware_tag,
+		    GB_FIRMWARE_U_TAG_MAX_SIZE);
 
 retry_fw_update:
 	backend_update.status = 0;
-- 
2.34.1

Re: [PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Dan Carpenter]

On Tue, Oct 14, 2025 at 01:41:48PM +0000, Vivek BalachandharTN wrote:
> strncpy() does not guarantee NUL-termination and is deprecated for
> NUL-terminated strings. Replace it with strscpy_pad(), which guarantees
> NUL-termination and zero-pads the remaining bytes, matching the fixed-size
> firmware tag semantics.
> 
> Signed-off-by: Vivek BalachandharTN <vivek.balachandhar@gmail.com>
> ---
>  .../greybus/Documentation/firmware/firmware.c        | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/greybus/Documentation/firmware/firmware.c b/drivers/staging/greybus/Documentation/firmware/firmware.c
> index 3b35ef6d4adb..deac8584841b 100644
> --- a/drivers/staging/greybus/Documentation/firmware/firmware.c
> +++ b/drivers/staging/greybus/Documentation/firmware/firmware.c

This is sample user space code so the strscpy_pad() isn't available.  It
will break the compile.

regards,
dan carpenter

Re: [PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Vivek BalachandharTN]

Yes, Dan. Nice catch. Building it with below sample change:

memset(&intf_load.firmware_tag, 0, GB_FIRMWARE_U_TAG_MAX_SIZE);
strncpy((char *)&intf_load.firmware_tag, firmware_tag,
         GB_FIRMWARE_U_TAG_MAX_SIZE - 1);

If it works, will send another patch.

Best, Vivek.


On 2025-10-14 9:53 a.m., Dan Carpenter wrote:
> On Tue, Oct 14, 2025 at 01:41:48PM +0000, Vivek BalachandharTN wrote:
>> strncpy() does not guarantee NUL-termination and is deprecated for
>> NUL-terminated strings. Replace it with strscpy_pad(), which guarantees
>> NUL-termination and zero-pads the remaining bytes, matching the fixed-size
>> firmware tag semantics.
>>
>> Signed-off-by: Vivek BalachandharTN <vivek.balachandhar@gmail.com>
>> ---
>>   .../greybus/Documentation/firmware/firmware.c        | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/staging/greybus/Documentation/firmware/firmware.c b/drivers/staging/greybus/Documentation/firmware/firmware.c
>> index 3b35ef6d4adb..deac8584841b 100644
>> --- a/drivers/staging/greybus/Documentation/firmware/firmware.c
>> +++ b/drivers/staging/greybus/Documentation/firmware/firmware.c
> This is sample user space code so the strscpy_pad() isn't available.  It
> will break the compile.
>
> regards,
> dan carpenter
>

Re: [PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Dan Carpenter]

On Tue, Oct 14, 2025 at 10:01:28AM -0400, Vivek BalachandharTN wrote:
> Yes, Dan. Nice catch. Building it with below sample change:
> 
> memset(&intf_load.firmware_tag, 0, GB_FIRMWARE_U_TAG_MAX_SIZE);
> strncpy((char *)&intf_load.firmware_tag, firmware_tag,
>         GB_FIRMWARE_U_TAG_MAX_SIZE - 1);

There isn't a need to doing the memset()...

regards,
dan carpenter

Re: [PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Vivek BalachandharTN]

Hi Dan,

Thanks again—confirmed the structs are zero-initialized before the copy.

Would a minimal fix that guarantees NUL-termination be acceptable, e.g.:

strncpy((char *)&intf_load.firmware_tag, firmware_tag,
         GB_FIRMWARE_U_TAG_MAX_SIZE - 1);
((char *)&intf_load.firmware_tag)[GB_FIRMWARE_U_TAG_MAX_SIZE - 1] = '\0';

I can respin as v2 with the same change applied to the other two 
firmware_tag
fields.

Best regards,
Vivek

On 2025-10-14 10:15 a.m., Dan Carpenter wrote:
> On Tue, Oct 14, 2025 at 10:01:28AM -0400, Vivek BalachandharTN wrote:
>> Yes, Dan. Nice catch. Building it with below sample change:
>>
>> memset(&intf_load.firmware_tag, 0, GB_FIRMWARE_U_TAG_MAX_SIZE);
>> strncpy((char *)&intf_load.firmware_tag, firmware_tag,
>>          GB_FIRMWARE_U_TAG_MAX_SIZE - 1);
> There isn't a need to doing the memset()...
>
> regards,
> dan carpenter
>

Re: [PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Dan Carpenter]

On Tue, Oct 14, 2025 at 12:10:50PM -0400, Vivek BalachandharTN wrote:
> Hi Dan,
> 
> Thanks again—confirmed the structs are zero-initialized before the copy.
> 
> Would a minimal fix that guarantees NUL-termination be acceptable, e.g.:
> 
> strncpy((char *)&intf_load.firmware_tag, firmware_tag,
>         GB_FIRMWARE_U_TAG_MAX_SIZE - 1);
> ((char *)&intf_load.firmware_tag)[GB_FIRMWARE_U_TAG_MAX_SIZE - 1] = '\0';
> 
> I can respin as v2 with the same change applied to the other two
> firmware_tag
> fields.

Sorry, I should have explained this at the start...  The struct is
initialized to zero.  The strncpy() copies at most
"GB_FIRMWARE_U_TAG_MAX_SIZE - 1" characters, meaning we never copy
anything to the last character which stays as zero.

regards,
dan carpenter

Re: [PATCH] staging: greybus: documentation: replace strncpy() with strscpy_pad()

[Vivek BalachandharTN]

Hi Dan,

Thanks for clarifying. That makes sense — since the struct starts
zeroed and the last byte remains untouched, the current code is
already safe. I’ll drop this patch.

Appreciate the quick guidance.

Best
Vivek

On 2025-10-14 1:13 p.m., Dan Carpenter wrote:
> On Tue, Oct 14, 2025 at 12:10:50PM -0400, Vivek BalachandharTN wrote:
>> Hi Dan,
>>
>> Thanks again—confirmed the structs are zero-initialized before the copy.
>>
>> Would a minimal fix that guarantees NUL-termination be acceptable, e.g.:
>>
>> strncpy((char *)&intf_load.firmware_tag, firmware_tag,
>>          GB_FIRMWARE_U_TAG_MAX_SIZE - 1);
>> ((char *)&intf_load.firmware_tag)[GB_FIRMWARE_U_TAG_MAX_SIZE - 1] = '\0';
>>
>> I can respin as v2 with the same change applied to the other two
>> firmware_tag
>> fields.
> Sorry, I should have explained this at the start...  The struct is
> initialized to zero.  The strncpy() copies at most
> "GB_FIRMWARE_U_TAG_MAX_SIZE - 1" characters, meaning we never copy
> anything to the last character which stays as zero.
>
> regards,
> dan carpenter
>