KVM: use after free in kvm_ioctl_create_device()

We should move the ops->destroy(dev) after the list_del(&dev->vm_node)
so that we don't use "dev" after freeing it.

Fixes: a28ebea2adc4 ("KVM: Protect device ops->create and list_add with kvm->lock")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
static long kvm_dev_ioctl(struct file *filp,
			  unsigned int ioctl, unsigned long arg)
{
	long r = -EINVAL;

	switch (ioctl) {
	case KVM_GET_API_VERSION:
		if (arg)
			goto out;
		r = KVM_API_VERSION;
		break;
	case KVM_CREATE_VM:
		r = kvm_dev_ioctl_create_vm(arg);
		break;
	case KVM_CHECK_EXTENSION:
		r = kvm_vm_ioctl_check_extension_generic(NULL, arg);
		break;
	case KVM_GET_VCPU_MMAP_SIZE:
		if (arg)
			goto out;
		r = PAGE_SIZE;     /* struct kvm_run */
#ifdef CONFIG_X86
		r += PAGE_SIZE;    /* pio data page */
#endif
#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
		r += PAGE_SIZE;    /* coalesced mmio ring page */
#endif
		break;
	case KVM_TRACE_ENABLE:
	case KVM_TRACE_PAUSE:
	case KVM_TRACE_DISABLE:
		r = -EOPNOTSUPP;
		break;
	default:
		return kvm_arch_dev_ioctl(filp, ioctl, arg);
	}
out:
	return r;
}

static long kvm_dev_ioctl(struct file *filp,
			  unsigned int ioctl, unsigned long arg)
{
	long r = -EINVAL;

	switch (ioctl) {
	case KVM_GET_API_VERSION:
		if (arg)
			goto out;
		r = KVM_API_VERSION;
		break;
	case KVM_CREATE_VM:
		r = kvm_dev_ioctl_create_vm(arg);
		break;
	case KVM_CHECK_EXTENSION:
		r = kvm_vm_ioctl_check_extension_generic(NULL, arg);
		break;
	case KVM_GET_VCPU_MMAP_SIZE:
		if (arg)
			goto out;
		r = PAGE_SIZE;     /* struct kvm_run */
#ifdef CONFIG_X86
		r += PAGE_SIZE;    /* pio data page */
#endif
#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
		r += PAGE_SIZE;    /* coalesced mmio ring page */
#endif
		break;
	case KVM_TRACE_ENABLE:
	case KVM_TRACE_PAUSE:
	case KVM_TRACE_DISABLE:
		r = -EOPNOTSUPP;
		break;
	default:
		return kvm_arch_dev_ioctl(filp, ioctl, arg);
	}
out:
	return r;
}
