[bug report] netvsc: use ERR_PTR to avoid dereference issues

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Hello stephen hemminger,

The patch 9749fed5d43d: "netvsc: use ERR_PTR to avoid dereference
issues" from Jul 19, 2017, leads to the following static checker
warning:

	drivers/net/hyperv/rndis_filter.c:1344 rndis_filter_device_add()
	warn: passing zero to 'ERR_PTR'

drivers/net/hyperv/rndis_filter.c
  1300          ret = rndis_filter_query_device(rndis_device, net_device,
  1301                                          OID_GEN_RECEIVE_SCALE_CAPABILITIES,
  1302                                          &rsscap, &rsscap_size);
  1303          if (ret || rsscap.num_recv_que < 2)
                           ^^^^^^^^^^^^^^^^^^^^^^^
I think this used to be a success path, but now it leads to a NULL
dereference in the caller.  I guess we should set "ret = -ENOMEM;" here?

  1304                  goto out;
  1305  
  1306          /* This guarantees that num_possible_rss_qs <= num_online_cpus */
  1307          num_possible_rss_qs = min_t(u32, num_online_cpus(),
  1308                                      rsscap.num_recv_que);
  1309  
  1310          net_device->max_chn = min_t(u32, VRSS_CHANNEL_MAX, num_possible_rss_qs);
  1311  
  1312          /* We will use the given number of channels if available. */
  1313          net_device->num_chn = min(net_device->max_chn, device_info->num_chn);
  1314  
  1315          for (i = 0; i < ITAB_NUM; i++)
  1316                  rndis_device->rx_table[i] = ethtool_rxfh_indir_default(
  1317                                                  i, net_device->num_chn);
  1318  
  1319          atomic_set(&net_device->open_chn, 1);
  1320          vmbus_set_sc_create_callback(dev->channel, netvsc_sc_open);
  1321  
  1322          for (i = 1; i < net_device->num_chn; i++) {
  1323                  ret = netvsc_alloc_recv_comp_ring(net_device, i);
  1324                  if (ret) {
  1325                          while (--i != 0)
  1326                                  vfree(net_device->chan_table[i].mrc.slots);
  1327                          goto out;
  1328                  }
  1329          }
  1330  
  1331          for (i = 1; i < net_device->num_chn; i++)
  1332                  netif_napi_add(net, &net_device->chan_table[i].napi,
  1333                                 netvsc_poll, NAPI_POLL_WEIGHT);
  1334  
  1335          return net_device;
  1336  
  1337  out:
  1338          /* setting up multiple channels failed */
  1339          net_device->max_chn = 1;
  1340          net_device->num_chn = 1;
  1341  
  1342  err_dev_remv:
  1343          rndis_filter_device_remove(dev, net_device);
  1344          return ERR_PTR(ret);

regards,
dan carpenter
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