unsigned int blk_plug_queued_count(struct request_queue *q)
{
	struct blk_plug *plug;
	struct request *rq;
	struct list_head *plug_list;
	unsigned int ret = 0;

	plug = current->plug;
	if (!plug)
		goto out;

	if (q->mq_ops)
		plug_list = &plug->mq_list;
	else
		plug_list = &plug->list;

	list_for_each_entry(rq, plug_list, queuelist) {
		if (rq->q == q)
			ret++;
	}
out:
	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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.