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

[Jason Wang]

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.

Thanks


> I guess we could move the - 1 to the other side?
>
> 	msg->iova > U64_MAX - msg->size + 1 ||
>
> regards,
> dan carpenter