staging: speakup: Replace strncpy with memcpy

BugLink: https://bugs.launchpad.net/bugs/1811080

commit fd29edc7 upstream.

gcc 8.1.0 generates the following warnings.

drivers/staging/speakup/kobjects.c: In function 'punc_store':
drivers/staging/speakup/kobjects.c:522:2: warning:
	'strncpy' output truncated before terminating nul
	copying as many bytes from a string as its length
drivers/staging/speakup/kobjects.c:504:6: note: length computed here

drivers/staging/speakup/kobjects.c: In function 'synth_store':
drivers/staging/speakup/kobjects.c:391:2: warning:
	'strncpy' output truncated before terminating nul
	copying as many bytes from a string as its length
drivers/staging/speakup/kobjects.c:388:8: note: length computed here

Using strncpy() is indeed less than perfect since the length of data to
be copied has already been determined with strlen(). Replace strncpy()
with memcpy() to address the warning and optimize the code a little.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/staging/speakup/kobjects.c

@@ -387,7 +387,7 @@ static ssize_t synth_store(struct kobject *kobj, struct kobj_attribute *attr,
 	len = strlen(buf);
 	if (len < 2 || len > 9)
 		return -EINVAL;
-	strncpy(new_synth_name, buf, len);
+	memcpy(new_synth_name, buf, len);
 	if (new_synth_name[len - 1] == '\n')
 		len--;
 	new_synth_name[len] = '\0';
@@ -514,7 +514,7 @@ static ssize_t punc_store(struct kobject *kobj, struct kobj_attribute *attr,
 		return -EINVAL;
 	}
 
-	strncpy(punc_buf, buf, x);
+	memcpy(punc_buf, buf, x);
 
 	while (x && punc_buf[x - 1] == '\n')
 		x--;