static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
{
	int r;
	struct kvm_vcpu *vcpu;

	if (id >= KVM_MAX_VCPU_ID)
		return -EINVAL;

	mutex_lock(&kvm->lock);
	if (kvm->created_vcpus == KVM_MAX_VCPUS) {
		mutex_unlock(&kvm->lock);
		return -EINVAL;
	}

	kvm->created_vcpus++;
	mutex_unlock(&kvm->lock);

	vcpu = kvm_arch_vcpu_create(kvm, id);
	if (IS_ERR(vcpu)) {
		r = PTR_ERR(vcpu);
		goto vcpu_decrement;
	}

	preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);

	r = kvm_arch_vcpu_setup(vcpu);
	if (r)
		goto vcpu_destroy;

	r = kvm_create_vcpu_debugfs(vcpu);
	if (r)
		goto vcpu_destroy;

	mutex_lock(&kvm->lock);
	if (kvm_get_vcpu_by_id(kvm, id)) {
		r = -EEXIST;
		goto unlock_vcpu_destroy;
	}

	BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);

	/* Now it's all set up, let userspace reach it */
	kvm_get_kvm(kvm);
	r = create_vcpu_fd(vcpu);
	if (r < 0) {
		kvm_put_kvm(kvm);
		goto unlock_vcpu_destroy;
	}

	kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;

	/*
	 * Pairs with smp_rmb() in kvm_get_vcpu.  Write kvm->vcpus
	 * before kvm->online_vcpu's incremented value.
	 */
	smp_wmb();
	atomic_inc(&kvm->online_vcpus);

	mutex_unlock(&kvm->lock);
	kvm_arch_vcpu_postcreate(vcpu);
	return r;

unlock_vcpu_destroy:
	mutex_unlock(&kvm->lock);
	debugfs_remove_recursive(vcpu->debugfs_dentry);
vcpu_destroy:
	kvm_arch_vcpu_destroy(vcpu);
vcpu_decrement:
	mutex_lock(&kvm->lock);
	kvm->created_vcpus--;
	mutex_unlock(&kvm->lock);
	return r;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.