scsi: 3w-sas: 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.

This pattern of strncpy(dest, src, strlen(src)) is extremely bug-prone.
This pattern basically never results in NUL-terminated destination
strings unless `dest` was zero-initialized. The current implementation
may be accidentally correct as tw_dev is zero-allocated via:

	host = scsi_host_alloc(&driver_template, sizeof(TW_Device_Extension));
        ...
	tw_dev = shost_priv(host);

... wherein scsi_host_alloc() zero-allocates host:

        shost = kzalloc(sizeof(struct Scsi_Host) + privsize, GFP_KERNEL);

Also, further suggesting this change is worthwhile is another strscpy()
usage in 3w-9xxx.c:

	strscpy(tw_dev->tw_compat_info.driver_version, TW_DRIVER_VERSION,
		sizeof(tw_dev->tw_compat_info.driver_version));

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.

Let's not be accidentally correct, let's be definitely correct.

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
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20231023-strncpy-drivers-scsi-3w-sas-c-v1-1-4c40a1e99dfc@google.com
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/3w-sas.c b/drivers/scsi/3w-sas.c
index 55989eaa2d9f1e35ebd869217e598d75f898bbb9..9bdb75dfdcd7c0a35c9880eabf140e145b842a41 100644 (file)
--- a/drivers/scsi/3w-sas.c
+++ b/drivers/scsi/3w-sas.c
@@ -1326,7 +1326,8 @@ static int twl_reset_sequence(TW_Device_Extension *tw_dev, int soft_reset)
                }
 
                /* Load rest of compatibility struct */
-               strncpy(tw_dev->tw_compat_info.driver_version, TW_DRIVER_VERSION, strlen(TW_DRIVER_VERSION));
+               strscpy(tw_dev->tw_compat_info.driver_version, TW_DRIVER_VERSION,
+                       sizeof(tw_dev->tw_compat_info.driver_version));
                tw_dev->tw_compat_info.driver_srl_high = TW_CURRENT_DRIVER_SRL;
                tw_dev->tw_compat_info.driver_branch_high = TW_CURRENT_DRIVER_BRANCH;
                tw_dev->tw_compat_info.driver_build_high = TW_CURRENT_DRIVER_BUILD;