sfc: 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.

`desc` is expected to be NUL-terminated as evident by the manual
NUL-byte assignment. Moreover, NUL-padding does not seem to be
necessary.

The only caller of efx_mcdi_nvram_metadata() is
efx_devlink_info_nvram_partition() which provides a NULL for `desc`:
|       rc = efx_mcdi_nvram_metadata(efx, partition_type, NULL, version, NULL, 0);

Due to this, I am not sure this code is even reached but we should still
favor something other than strncpy.

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.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Signed-off-by: Justin Stitt <justinstitt@google.com>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231012-strncpy-drivers-net-ethernet-sfc-mcdi-c-v1-1-478c8de1039d@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c
index d23da962733890e52c869977d4790e6bdbf30243..76578502226ed5b8dc898a90c4ee292648547ba2 100644 (file)
--- a/drivers/net/ethernet/sfc/mcdi.c
+++ b/drivers/net/ethernet/sfc/mcdi.c
@@ -2205,10 +2205,9 @@ int efx_mcdi_nvram_metadata(struct efx_nic *efx, unsigned int type,
                                goto out_free;
                        }
 
-                       strncpy(desc,
+                       strscpy(desc,
                                MCDI_PTR(outbuf, NVRAM_METADATA_OUT_DESCRIPTION),
                                MC_CMD_NVRAM_METADATA_OUT_DESCRIPTION_NUM(outlen));
-                       desc[MC_CMD_NVRAM_METADATA_OUT_DESCRIPTION_NUM(outlen)] = '\0';
                } else {
                        desc[0] = '\0';
                }