[bug report] liquidio: fix for iq and droq cnts going negative

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Satanand Burla,

This is a semi-automatic email about new static checker warnings.

The patch cdb478e5e413: "liquidio: fix for iq and droq cnts going 
negative" from Jan 31, 2017, leads to the following Smatch complaint:

drivers/net/ethernet/cavium/liquidio/lio_main.c:2450 liquidio_napi_poll()
	 error: we previously assumed 'iq' could be null (see line 2436)

drivers/net/ethernet/cavium/liquidio/lio_main.c
  2435		iq = oct->instr_queue[iq_no];
  2436		if (iq) {
                    ^^
Old code assumed "iq" can be NULL.

  2437			/* Process iq buffers with in the budget limits */
  2438			tx_done = octeon_flush_iq(oct, iq, budget);
  2439			/* Update iq read-index rather than waiting for next interrupt.
  2440			 * Return back if tx_done is false.
  2441			 */
  2442			update_txq_status(oct, iq_no);
  2443		} else {
  2444			dev_err(&oct->pci_dev->dev, "%s:  iq (%d) num invalid\n",
  2445				__func__, iq_no);
  2446		}
  2447	
  2448		/* force enable interrupt if reg cnts are high to avoid wraparound */
  2449		if ((work_done < budget && tx_done) ||
  2450		    (iq->pkt_in_done >= MAX_REG_CNT) ||
                     ^^^^^^^^^^^^^^^
New code adds unchecked dereference.

  2451		    (droq->pkt_count >= MAX_REG_CNT)) {
  2452			tx_done = 1;

regards,
dan carpenter