void kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
	ktime_t start, cur;
	DECLARE_SWAITQUEUE(wait);
	bool waited = false;
	u64 block_ns;

	start = cur = ktime_get();
	if (vcpu->halt_poll_ns) {
		ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);

		++vcpu->stat.halt_attempted_poll;
		do {
			/*
			 * This sets KVM_REQ_UNHALT if an interrupt
			 * arrives.
			 */
			if (kvm_vcpu_check_block(vcpu) < 0) {
				++vcpu->stat.halt_successful_poll;
				if (!vcpu_valid_wakeup(vcpu))
					++vcpu->stat.halt_poll_invalid;
				goto out;
			}
			cur = ktime_get();
		} while (single_task_running() && ktime_before(cur, stop));
	}

	kvm_arch_vcpu_blocking(vcpu);

	for (;;) {
		prepare_to_swait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);

		if (kvm_vcpu_check_block(vcpu) < 0)
			break;

		waited = true;
		schedule();
	}

	finish_swait(&vcpu->wq, &wait);
	cur = ktime_get();

	kvm_arch_vcpu_unblocking(vcpu);
out:
	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);

	if (!vcpu_valid_wakeup(vcpu))
		shrink_halt_poll_ns(vcpu);
	else if (halt_poll_ns) {
		if (block_ns <= vcpu->halt_poll_ns)
			;
		/* we had a long block, shrink polling */
		else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
			shrink_halt_poll_ns(vcpu);
		/* we had a short halt and our poll time is too small */
		else if (vcpu->halt_poll_ns < halt_poll_ns &&
			block_ns < halt_poll_ns)
			grow_halt_poll_ns(vcpu);
	} else
		vcpu->halt_poll_ns = 0;

	trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
	kvm_arch_vcpu_block_finish(vcpu);
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.