int mlx4_register_vlan(struct mlx4_dev *dev, u8 port, u16 vlan, int *index)
{
	struct mlx4_vlan_table *table = &mlx4_priv(dev)->port[port].vlan_table;
	int i, err = 0;
	int free = -1;

	mutex_lock(&table->mutex);
	for (i = MLX4_VLAN_REGULAR; i < MLX4_MAX_VLAN_NUM; i++) {
		if (free < 0 && (table->refs[i] == 0)) {
			free = i;
			continue;
		}

		if (table->refs[i] &&
		    (vlan == (MLX4_VLAN_MASK &
			      be32_to_cpu(table->entries[i])))) {
			/* Vlan already registered, increase refernce count */
			*index = i;
			++table->refs[i];
			goto out;
		}
	}

	if (free < 0) {
		err = -ENOMEM;
		goto out;
	}

	if (table->total == table->max) {
		/* No free vlan entries */
		err = -ENOSPC;
		goto out;
	}

	/* Register new MAC */
	table->refs[free] = 1;
	table->entries[free] = cpu_to_be32(vlan | MLX4_VLAN_VALID);

	err = mlx4_set_port_vlan_table(dev, port, table->entries);
	if (unlikely(err)) {
		mlx4_warn(dev, "Failed adding vlan: %u\n", vlan);
		table->refs[free] = 0;
		table->entries[free] = 0;
		goto out;
	}

	*index = free;
	++table->total;
out:
	mutex_unlock(&table->mutex);
	return err;
}
The software performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.