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

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:

quoted

On Wed, Jul 14, 2021 at 10:14:32AM +0800, Jason Wang wrote:

quoted

在 2021/7/13 下午7:31, Dan Carpenter 写道:

quoted

On Tue, Jul 13, 2021 at 04:46:52PM +0800, Xie Yongji wrote:

quoted

@@ -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.

quoted

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).

regards,
dan carpenter