void blk_set_queue_dying(struct request_queue *q)
{
	blk_queue_flag_set(QUEUE_FLAG_DYING, q);

	/*
	 * When queue DYING flag is set, we need to block new req
	 * entering queue, so we call blk_freeze_queue_start() to
	 * prevent I/O from crossing blk_queue_enter().
	 */
	blk_freeze_queue_start(q);

	if (q->mq_ops)
		blk_mq_wake_waiters(q);
	else {
		struct request_list *rl;

		spin_lock_irq(q->queue_lock);
		blk_queue_for_each_rl(rl, q) {
			if (rl->rq_pool) {
				wake_up_all(&rl->wait[BLK_RW_SYNC]);
				wake_up_all(&rl->wait[BLK_RW_ASYNC]);
			}
		}
		spin_unlock_irq(q->queue_lock);
	}

	/* Make blk_queue_enter() reexamine the DYING flag. */
	wake_up_all(&q->mq_freeze_wq);
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.