static int bsg_put_device(struct bsg_device *bd)
{
	int ret = 0, do_free;
	struct request_queue *q = bd->queue;

	mutex_lock(&bsg_mutex);

	do_free = atomic_dec_and_test(&bd->ref_count);
	if (!do_free) {
		mutex_unlock(&bsg_mutex);
		goto out;
	}

	hlist_del(&bd->dev_list);
	mutex_unlock(&bsg_mutex);

	dprintk("%s: tearing down\n", bd->name);

	/*
	 * close can always block
	 */
	set_bit(BSG_F_BLOCK, &bd->flags);

	/*
	 * correct error detection baddies here again. it's the responsibility
	 * of the app to properly reap commands before close() if it wants
	 * fool-proof error detection
	 */
	ret = bsg_complete_all_commands(bd);

	kfree(bd);
out:
	kref_put(&q->bsg_dev.ref, bsg_kref_release_function);
	if (do_free)
		blk_put_queue(q);
	return ret;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.