On Tue, Jul 13, 2021 at 7:31 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> 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()
>
> 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 ||
> msg->iova + msg->size - 1 > v->range.last)
>
Make sense.
> 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.
>
OK, I will send a patch to fix it.
Thanks,
Yongji
