inline void __blk_run_queue_uncond(struct request_queue *q)
{
	lockdep_assert_held(q->queue_lock);
	WARN_ON_ONCE(q->mq_ops);

	if (unlikely(blk_queue_dead(q)))
		return;

	/*
	 * Some request_fn implementations, e.g. scsi_request_fn(), unlock
	 * the queue lock internally. As a result multiple threads may be
	 * running such a request function concurrently. Keep track of the
	 * number of active request_fn invocations such that blk_drain_queue()
	 * can wait until all these request_fn calls have finished.
	 */
	q->request_fn_active++;
	q->request_fn(q);
	q->request_fn_active--;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.