usb: hso: check for return value in hso_serial_common_create()

in case of an error tty_register_device_attr() returns ERR_PTR(),
add IS_ERR() check

Reported-and-tested-by: syzbot+67b2bd0e34f952d0321e@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=67b2bd0e34f952d0321eSigned-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/hso.c

@@ -2261,12 +2261,14 @@ static int hso_serial_common_create(struct hso_serial *serial, int num_urbs,
 
 	minor = get_free_serial_index();
 	if (minor < 0)
-		goto exit;
+		goto exit2;
 
 	/* register our minor number */
 	serial->parent->dev = tty_port_register_device_attr(&serial->port,
 			tty_drv, minor, &serial->parent->interface->dev,
 			serial->parent, hso_serial_dev_groups);
+	if (IS_ERR(serial->parent->dev))
+		goto exit2;
 
 	/* fill in specific data for later use */
 	serial->minor = minor;
@@ -2311,6 +2313,7 @@ static int hso_serial_common_create(struct hso_serial *serial, int num_urbs,
 	return 0;
 exit:
 	hso_serial_tty_unregister(serial);
+exit2:
 	hso_serial_common_free(serial);
 	return -1;
 }