kernfs: Replace strncpy with memcpy

BugLink: https://bugs.launchpad.net/bugs/1811077

commit 166126c1 upstream.

gcc 8.1.0 complains:

fs/kernfs/symlink.c:91:3: warning:
	'strncpy' output truncated before terminating nul copying
	as many bytes from a string as its length
fs/kernfs/symlink.c: In function 'kernfs_iop_get_link':
fs/kernfs/symlink.c:88:14: 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>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/kernfs/symlink.c

@@ -88,7 +88,7 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
 		int slen = strlen(kn->name);
 
 		len -= slen;
-		strncpy(s + len, kn->name, slen);
+		memcpy(s + len, kn->name, slen);
 		if (len)
 			s[--len] = '/';