scsi: ibmvscsi_tgt: Replace deprecated strncpy() with strscpy()

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 don't need the NUL-padding behavior that strncpy() provides as vscsi is
NUL-allocated in ibmvscsis_probe() which proceeds to call
ibmvscsis_adapter_info():

|       vscsi = kzalloc(sizeof(*vscsi), GFP_KERNEL);

ibmvscsis_probe() -> ibmvscsis_handle_crq() -> ibmvscsis_parse_command()
-> ibmvscsis_mad() -> ibmvscsis_process_mad() -> ibmvscsis_adapter_info()

Following the same idea, `partition_name` is defiend as:

|       static char partition_name[PARTITION_NAMELEN] = "UNKNOWN";
... which is NUL-padded already, meaning strscpy() is the best option.

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.

However, for cap->name and info let's use strscpy_pad() as they are
allocated via dma_alloc_coherent():

|       cap = dma_alloc_coherent(&vscsi->dma_dev->dev, olen, &token,
|                                GFP_ATOMIC);
&
|       info = dma_alloc_coherent(&vscsi->dma_dev->dev, sizeof(*info), &token,
|                                 GFP_ATOMIC);

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>
Link: https://lore.kernel.org/r/20231212-strncpy-drivers-scsi-ibmvscsi_tgt-ibmvscsi_tgt-c-v2-1-bdb9a7cd96c8@google.com


Acked-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>