staging: hv: fix the page buffer when rndis data go across page boundary

In rndis_filter_receive_data(), we need to drop the 0th page and move the
rest of pages forward if the rndis data go across page boundary, otherwise
the page offset will overflow.
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/rndis_filter.c

@@ -323,6 +323,7 @@ static void rndis_filter_receive_data(struct rndis_device *dev,
 {
 	struct rndis_packet *rndis_pkt;
 	u32 data_offset;
+	int i;
 
 	rndis_pkt = &msg->msg.pkt;
 
@@ -338,6 +339,15 @@ static void rndis_filter_receive_data(struct rndis_device *dev,
 	pkt->page_buf[0].offset += data_offset;
 	pkt->page_buf[0].len -= data_offset;
 
+	/* Drop the 0th page, if rndis data go beyond page boundary */
+	if (pkt->page_buf[0].offset >= PAGE_SIZE) {
+		pkt->page_buf[1].offset = pkt->page_buf[0].offset - PAGE_SIZE;
+		pkt->page_buf[1].len -= pkt->page_buf[1].offset;
+		pkt->page_buf_cnt--;
+		for (i = 0; i < pkt->page_buf_cnt; i++)
+			pkt->page_buf[i] = pkt->page_buf[i+1];
+	}
+
 	pkt->is_data_pkt = true;
 
 	netvsc_recv_callback(dev->net_dev->dev, pkt);