sysfs: Fix regression when adding a file to an existing group

Commit 5f81880 ("sysfs, kobject: allow creating kobject belonging
to arbitrary users") incorrectly changed the argument passed as the
parent parameter when calling sysfs_add_file_mode_ns(). This caused some
sysfs attribute files to not be added correctly to certain groups.

Fixes: 5f81880 ("sysfs, kobject: allow creating kobject belonging to arbitrary users")
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Tested-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/sysfs/file.c

@@ -373,7 +373,7 @@ int sysfs_add_file_to_group(struct kobject *kobj,
 		return -ENOENT;
 
 	kobject_get_ownership(kobj, &uid, &gid);
-	error = sysfs_add_file_mode_ns(kobj->sd, attr, false,
+	error = sysfs_add_file_mode_ns(parent, attr, false,
 				       attr->mode, uid, gid, NULL);
 	kernfs_put(parent);