[PATCH v3 5/7] scsi: devinfo: replace strncpy and manual pad

[Justin Stitt <justinstitt@google.com>]

Depending on the state of @compatible, we are going to do different
things with our @to buffer.

When @compatible is true we want a NUL-term'd and NUL-padded destination
buffer. Conversely, if @compatible is false we just want a space-padded
destination buffer (no NUL-term required).

As per:
/**
 * scsi_dev_info_list_add_keyed - add one dev_info list entry.
 * @compatible: if true, null terminate short strings.  Otherwise space pad.
...

Note that we can't easily use `strtomem_pad` here as the size of the @to
buffer is unknown to the compiler due to indirection layers.

Now, the intent of the code is more clear (I probably didn't even need
to add a comment -- that's how clear it is).

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
 drivers/scsi/scsi_devinfo.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
index 3fcaf10a9dfe..2d3dbce25629 100644
--- a/drivers/scsi/scsi_devinfo.c
+++ b/drivers/scsi/scsi_devinfo.c
@@ -293,14 +293,16 @@ static void scsi_strcpy_devinfo(char *name, char *to, size_t to_length,
 	size_t from_length;
 
 	from_length = strlen(from);
-	/* This zero-pads the destination */
-	strncpy(to, from, to_length);
-	if (from_length < to_length && !compatible) {
-		/*
-		 * space pad the string if it is short.
-		 */
-		memset(&to[from_length], ' ', to_length - from_length);
-	}
+
+	/*
+	 * null pad and null terminate if compatible
+	 * otherwise space pad
+	 */
+	if (compatible)
+		strscpy_pad(to, from, to_length);
+	else
+		memcpy_and_pad(to, to_length, from, from_length, ' ');
+
 	if (from_length > to_length)
 		 printk(KERN_WARNING "%s: %s string '%s' is too long\n",
 			__func__, name, from);

-- 
2.44.0.278.ge034bb2e1d-goog