static struct request *get_request(struct request_queue *q, unsigned int op,
		struct bio *bio, blk_mq_req_flags_t flags, gfp_t gfp)
{
	const bool is_sync = op_is_sync(op);
	DEFINE_WAIT(wait);
	struct request_list *rl;
	struct request *rq;

	lockdep_assert_held(q->queue_lock);
	WARN_ON_ONCE(q->mq_ops);

	rl = blk_get_rl(q, bio);	/* transferred to @rq on success */
retry:
	rq = __get_request(rl, op, bio, flags, gfp);
	if (!IS_ERR(rq))
		return rq;

	if (op & REQ_NOWAIT) {
		blk_put_rl(rl);
		return ERR_PTR(-EAGAIN);
	}

	if ((flags & BLK_MQ_REQ_NOWAIT) || unlikely(blk_queue_dying(q))) {
		blk_put_rl(rl);
		return rq;
	}

	/* wait on @rl and retry */
	prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
				  TASK_UNINTERRUPTIBLE);

	trace_block_sleeprq(q, bio, op);

	spin_unlock_irq(q->queue_lock);
	io_schedule();

	/*
	 * After sleeping, we become a "batching" process and will be able
	 * to allocate at least one request, and up to a big batch of them
	 * for a small period time.  See ioc_batching, ioc_set_batching
	 */
	ioc_set_batching(q, current->io_context);

	spin_lock_irq(q->queue_lock);
	finish_wait(&rl->wait[is_sync], &wait);

	goto retry;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.