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

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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





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