[bug report] net/smc: fix ethernet interface refcounting

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Ursula Braun,

The patch 98f3375505b8: "net/smc: fix ethernet interface refcounting"
from Nov 6, 2019, leads to the following static checker warning:

	net/smc/smc_pnet.c:379 smc_pnet_fill_entry()
	warn: 'pnetelem->ndev' held on error path.

net/smc/smc_pnet.c
   329  static int smc_pnet_fill_entry(struct net *net,
   330                                 struct smc_user_pnetentry *pnetelem,
   331                                 struct nlattr *tb[])
   332  {
   333          char *string, *ibname;
   334          int rc;
   335  
   336          memset(pnetelem, 0, sizeof(*pnetelem));
   337          INIT_LIST_HEAD(&pnetelem->list);
   338  
   339          rc = -EINVAL;
   340          if (!tb[SMC_PNETID_NAME])
   341                  goto error;
   342          string = (char *)nla_data(tb[SMC_PNETID_NAME]);
   343          if (!smc_pnetid_valid(string, pnetelem->pnet_name))
   344                  goto error;
   345  
   346          rc = -EINVAL;
   347          if (tb[SMC_PNETID_ETHNAME]) {
   348                  string = (char *)nla_data(tb[SMC_PNETID_ETHNAME]);
   349                  pnetelem->ndev = dev_get_by_name(net, string);
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
dev_hold().

   350                  if (!pnetelem->ndev)
   351                          goto error;
   352          }
   353  
   354          /* if this is not the initial namespace, stop here */
   355          if (net != &init_net)
   356                  return 0;
   357  
   358          rc = -EINVAL;
   359          if (tb[SMC_PNETID_IBNAME]) {
   360                  ibname = (char *)nla_data(tb[SMC_PNETID_IBNAME]);
   361                  ibname = strim(ibname);
   362                  pnetelem->smcibdev = smc_pnet_find_ib(ibname);
   363                  pnetelem->smcd_dev = smc_pnet_find_smcd(ibname);
   364                  if (!pnetelem->smcibdev && !pnetelem->smcd_dev)
   365                          goto error;
                                ^^^^^^^^^^
Smatch thinks these require dev_put()

   366                  if (pnetelem->smcibdev) {
   367                          if (!tb[SMC_PNETID_IBPORT])
   368                                  goto error;
   369                          pnetelem->ib_port = nla_get_u8(tb[SMC_PNETID_IBPORT]);
   370                          if (pnetelem->ib_port < 1 ||
   371                              pnetelem->ib_port > SMC_MAX_PORTS)
   372                                  goto error;
                                        ^^^^^^^^^^
   373                  }
   374          }
   375  
   376          return 0;
   377  
   378  error:

So maybe this should be:

	if (pnetelem->ndev && tb[SMC_PNETID_ETHNAME])
		dev_put(pnetelem->ndev);

   379          return rc;
   380  }

regards,
dan carpenter