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

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

On Fri, Dec 21, 2018 at 11:40:36AM +0800, liuyonglong wrote:
> Hi, Dan Carpenter:
> 
> On 2018/12/20 17:46, Dan Carpenter wrote:
> > 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.
> > 
> 
> set_promisc_tcam_enable is only called by hns_dsaf_set_promisc_tcam,
> and hns_dsaf_set_promisc_tcam is only called by hns_mac_set_promisc.
> hns_mac_set_promisc pass "mac_cb->mac_id" to the parameter "port", so the range of "port" is equals to "mac_cb->mac_id".
> 
> When hns_mac_init, "mac_cb->mac_id" is limited to smaller than 6, so it's no problem.

If it's 6 then it is one element past the end of the array.

> 
> So maybe this case "port >= DSAF_BASE_INNER_PORT_NUM" can never touch, need delete.
> 
> I wanna know if u just test this function only, and pass 127 to the parameter "port"?
> 

This is from static analysis not testing.  Also I looked lower in the
function and just removing the conditions is not enough to fix the bugs.

  2821  
  2822          if (port < DSAF_SERVICE_NW_NUM) {
  2823                  mskid = port;
  2824          } else if (port >= DSAF_BASE_INNER_PORT_NUM) {
  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          }
  2832  
  2833          dsaf_set_bit(tbl_tcam_mcast.tbl_mcast_port_msk[mskid / 32],
                                                               ^^^^^^^^^^
Since mskid is alway 0-5, that means that mskid / 32 is always zero.

  2834                       mskid % 32, 1);
  2835          memcpy(&temp_key, &mask_key, sizeof(mask_key));
  2836          hns_dsaf_tcam_mc_cfg_vague(dsaf_dev, entry_index, &tbl_tcam_data_mc,
  2837                                     (struct dsaf_tbl_tcam_data *)(&mask_key),
  2838                                     &tbl_tcam_mcast);
  2839  

regards,
dan carpenter