[bug report] net: hns: Fix ping failed when use net bridge and send multicast

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

Hello Yonglong Liu,

The patch 6adafc356e20: "net: hns: Fix ping failed when use net
bridge and send multicast" from Dec 15, 2018, leads to the following
static checker warning:

	drivers/net/ethernet/hisilicon/hns/hns_dsaf_main.c:2822 set_promisc_tcam_enable()
	error: testing array offset 'port' after use.

drivers/net/ethernet/hisilicon/hns/hns_dsaf_main.c
  2786  
  2787          mac_cb = dsaf_dev->mac_cb[port];
                                   ^^^^^^^^^^^^
The ->mac_cb[] array has 6 elements.

  2788          (void)hns_mac_get_inner_port_num(mac_cb, 0, &port_num);
  2789          tbl_tcam_ucast.tbl_ucast_out_port = port_num;
  2790  
  2791          /* config uc vague table */
  2792          hns_dsaf_tcam_uc_cfg_vague(dsaf_dev, entry_index, &tbl_tcam_data_uc,
  2793                                     &tbl_tcam_mask_uc, &tbl_tcam_ucast);
  2794  
  2795          /* update software entry */
  2796          soft_mac_entry = priv->soft_mac_tbl;
  2797          soft_mac_entry += entry_index;
  2798          soft_mac_entry->index = entry_index;
  2799          soft_mac_entry->tcam_key.high.val = mac_key.high.val;
  2800          soft_mac_entry->tcam_key.low.val = mac_key.low.val;
  2801          /* step back to the START for mc. */
  2802          soft_mac_entry = priv->soft_mac_tbl;
  2803  
  2804          /* 2. set promisc multicast vague tcam entry. */
  2805          entry_index = hns_dsaf_find_empty_mac_entry_reverse(dsaf_dev);
  2806          if (entry_index = DSAF_INVALID_ENTRY_IDX) {
  2807                  dev_err(dsaf_dev->dev,
  2808                          "enable mc promisc failed (port:%#x)\n",
  2809                          port);
  2810                  return;
  2811          }
  2812  
  2813          memset(&mask_entry, 0x0, sizeof(mask_entry));
  2814          memset(&mask_key, 0x0, sizeof(mask_key));
  2815          memset(&temp_key, 0x0, sizeof(temp_key));
  2816          mask_entry.addr[0] = 0x01;
  2817          hns_dsaf_set_mac_key(dsaf_dev, &mask_key, mask_entry.in_vlan_id,
  2818                               port, mask_entry.addr);
  2819          tbl_tcam_mcast.tbl_mcast_item_vld = 1;
  2820          tbl_tcam_mcast.tbl_mcast_old_en = 0;
  2821  
  2822          if (port < DSAF_SERVICE_NW_NUM) {
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^

  2823                  mskid = port;
  2824          } else if (port >= DSAF_BASE_INNER_PORT_NUM) {
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Here we are testing if "port" is over 127 but we are so toasted if
that condition is true.

  2825                  mskid = port - DSAF_BASE_INNER_PORT_NUM + DSAF_SERVICE_NW_NUM;
  2826          } else {
  2827                  dev_err(dsaf_dev->dev, "%s,pnum(%d)error,key(%#x:%#x)\n",
  2828                          dsaf_dev->ae_dev.name, port,
  2829                          mask_key.high.val, mask_key.low.val);
  2830                  return;
  2831          }

regards,
dan carpenter