void blk_queue_bypass_start(struct request_queue *q)
{
	WARN_ON_ONCE(q->mq_ops);

	spin_lock_irq(q->queue_lock);
	q->bypass_depth++;
	queue_flag_set(QUEUE_FLAG_BYPASS, q);
	spin_unlock_irq(q->queue_lock);

	/*
	 * Queues start drained.  Skip actual draining till init is
	 * complete.  This avoids lenghty delays during queue init which
	 * can happen many times during boot.
	 */
	if (blk_queue_init_done(q)) {
		spin_lock_irq(q->queue_lock);
		__blk_drain_queue(q, false);
		spin_unlock_irq(q->queue_lock);

		/* ensure blk_queue_bypass() is %true inside RCU read lock */
		synchronize_rcu();
	}
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.