KVM: Validate userspace_addr of memslot when registered

This way, we can avoid checking the user space address many times when
we read the guest memory.

Although we can do the same for write if we check which slots are
writable, we do not care write now: reading the guest memory happens
more often than writing.

[avi: change VERIFY_READ to VERIFY_WRITE]

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
static struct kvm *kvm_create_vm(void)
{
	int r, i;
	struct kvm *kvm = kvm_arch_alloc_vm();

	if (!kvm)
		return ERR_PTR(-ENOMEM);

	r = kvm_arch_init_vm(kvm);
	if (r)
		goto out_err_nodisable;

	r = hardware_enable_all();
	if (r)
		goto out_err_nodisable;

#ifdef CONFIG_HAVE_KVM_IRQCHIP
	INIT_HLIST_HEAD(&kvm->mask_notifier_list);
	INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif

	r = -ENOMEM;
	kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
	if (!kvm->memslots)
		goto out_err_nosrcu;
	if (init_srcu_struct(&kvm->srcu))
		goto out_err_nosrcu;
	for (i = 0; i < KVM_NR_BUSES; i++) {
		kvm->buses[i] = kzalloc(sizeof(struct kvm_io_bus),
					GFP_KERNEL);
		if (!kvm->buses[i])
			goto out_err;
	}

	r = kvm_init_mmu_notifier(kvm);
	if (r)
		goto out_err;

	kvm->mm = current->mm;
	atomic_inc(&kvm->mm->mm_count);
	spin_lock_init(&kvm->mmu_lock);
	kvm_eventfd_init(kvm);
	mutex_init(&kvm->lock);
	mutex_init(&kvm->irq_lock);
	mutex_init(&kvm->slots_lock);
	atomic_set(&kvm->users_count, 1);
	raw_spin_lock(&kvm_lock);
	list_add(&kvm->vm_list, &vm_list);
	raw_spin_unlock(&kvm_lock);

	return kvm;

out_err:
	cleanup_srcu_struct(&kvm->srcu);
out_err_nosrcu:
	hardware_disable_all();
out_err_nodisable:
	for (i = 0; i < KVM_NR_BUSES; i++)
		kfree(kvm->buses[i]);
	kfree(kvm->memslots);
	kvm_arch_free_vm(kvm);
	return ERR_PTR(r);
}

static struct kvm *kvm_create_vm(void)
{
	int r, i;
	struct kvm *kvm = kvm_arch_alloc_vm();

	if (!kvm)
		return ERR_PTR(-ENOMEM);

	r = kvm_arch_init_vm(kvm);
	if (r)
		goto out_err_nodisable;

	r = hardware_enable_all();
	if (r)
		goto out_err_nodisable;

#ifdef CONFIG_HAVE_KVM_IRQCHIP
	INIT_HLIST_HEAD(&kvm->mask_notifier_list);
	INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif

	r = -ENOMEM;
	kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
	if (!kvm->memslots)
		goto out_err_nosrcu;
	if (init_srcu_struct(&kvm->srcu))
		goto out_err_nosrcu;
	for (i = 0; i < KVM_NR_BUSES; i++) {
		kvm->buses[i] = kzalloc(sizeof(struct kvm_io_bus),
					GFP_KERNEL);
		if (!kvm->buses[i])
			goto out_err;
	}

	r = kvm_init_mmu_notifier(kvm);
	if (r)
		goto out_err;

	kvm->mm = current->mm;
	atomic_inc(&kvm->mm->mm_count);
	spin_lock_init(&kvm->mmu_lock);
	kvm_eventfd_init(kvm);
	mutex_init(&kvm->lock);
	mutex_init(&kvm->irq_lock);
	mutex_init(&kvm->slots_lock);
	atomic_set(&kvm->users_count, 1);
	raw_spin_lock(&kvm_lock);
	list_add(&kvm->vm_list, &vm_list);
	raw_spin_unlock(&kvm_lock);

	return kvm;

out_err:
	cleanup_srcu_struct(&kvm->srcu);
out_err_nosrcu:
	hardware_disable_all();
out_err_nodisable:
	for (i = 0; i < KVM_NR_BUSES; i++)
		kfree(kvm->buses[i]);
	kfree(kvm->memslots);
	kvm_arch_free_vm(kvm);
	return ERR_PTR(r);
}
