Re: [PATCH v9 13/17] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap()

[Jason Wang]

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?

Thanks


> 	    msg->iova + msg->size - 1 > v->range.last)
>
> But writing integer overflow check correctly is notoriously difficult.
> Do you think you could send a fix for that which is separate from the
> patcheset?  We'd want to backport it to stable.
>
> regards,
> dan carpenter