# Re: \[PATCH v9 13/17\] vdpa: factor out vhost\_vdpa\_pa\_map() and vhost\_vdpa\_pa\_unmap()

- From: Jason Wang \<hidden\>
- Date: 2021-07-15 02:21:12 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/07/209938
- Thread: https://ratatoskr.run/netdev/2021/07/209755/t.md

```text

在 2021/7/14 下午5:57, Dan Carpenter 写道:
> On Wed, Jul 14, 2021 at 05:41:54PM +0800, Jason Wang wrote:
>> 在 2021/7/14 下午4:05, Dan Carpenter 写道:
>>> On Wed, Jul 14, 2021 at 10:14:32AM +0800, Jason Wang wrote:
>>>> 在 2021/7/13 下午7:31, Dan Carpenter 写道:
>>>>> On Tue, Jul 13, 2021 at 04:46:52PM +0800, Xie Yongji wrote:
>>>>>> @@ -613,37 +618,28 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v, u64 iova, u64 size)
>>>>>>     	}
>>>>>>     }
>>>>>> -static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>>>>>> -					   struct vhost_iotlb_msg *msg)
>>>>>> +static int vhost_vdpa_pa_map(struct vhost_vdpa *v,
>>>>>> +			     u64 iova, u64 size, u64 uaddr, u32 perm)
>>>>>>     {
>>>>>>     	struct vhost_dev *dev = &v->vdev;
>>>>>> -	struct vhost_iotlb *iotlb = dev->iotlb;
>>>>>>     	struct page **page_list;
>>>>>>     	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
>>>>>>     	unsigned int gup_flags = FOLL_LONGTERM;
>>>>>>     	unsigned long npages, cur_base, map_pfn, last_pfn = 0;
>>>>>>     	unsigned long lock_limit, sz2pin, nchunks, i;
>>>>>> -	u64 iova = msg->iova;
>>>>>> +	u64 start = iova;
>>>>>>     	long pinned;
>>>>>>     	int ret = 0;
>>>>>> -	if (msg->iova < v->range.first ||
>>>>>> -	    msg->iova + msg->size - 1 > v->range.last)
>>>>>> -		return -EINVAL;
>>>>> This is not related to your patch, but can the "msg->iova + msg->size"
>>>>> addition can have an integer overflow.  From looking at the callers it
>>>>> seems like it can.  msg comes from:
>>>>>      vhost_chr_write_iter()
>>>>>      --> dev->msg_handler(dev, &msg);
>>>>>          --> vhost_vdpa_process_iotlb_msg()
>>>>>             --> vhost_vdpa_process_iotlb_update()
>>>> Yes.
>>>>
>>>>
>>>>> If I'm thinking of the right thing then these are allowed to overflow to
>>>>> 0 because of the " - 1" but not further than that.  I believe the check
>>>>> needs to be something like:
>>>>>
>>>>> 	if (msg->iova < v->range.first ||
>>>>> 	    msg->iova - 1 > U64_MAX - msg->size ||
>>>> I guess we don't need - 1 here?
>>> The - 1 is important.  The highest address is 0xffffffff.  So it goes
>>> start + size = 0 and then start + size - 1 == 0xffffffff.
>>
>> Right, so actually
>>
>> msg->iova = 0xfffffffe, msg->size=2 is valid.
> I believe so, yes.  It's inclusive of 0xfffffffe and 0xffffffff.
> (Not an expert).


I think so, and we probably need to fix vhost_overflow() as well which did:

static bool vhost_overflow(u64 uaddr, u64 size)
{
        /* Make sure 64 bit math will not overflow. */
        return uaddr > ULONG_MAX || size > ULONG_MAX || uaddr > ULONG_MAX - size;
}

Thanks


>
> regards,
> dan carpenter
>

```