Re: [PATCH net-next v17 11/14] net: ethtool: cable-test: Target the command to the requested PHY

[Dan Carpenter <dan.carpenter@linaro.org>]

On Tue, Aug 27, 2024 at 07:33:59AM +0200, Maxime Chevallier wrote:
> 
> This issue has indeed been detected, and is being addressed, see :
> 
> https://lore.kernel.org/netdev/20240826134656.94892-1-djahchankoike@gmail.com/
> 

There is a similar bug in ethnl_act_cable_test_tdr() that needs to be fixed
as well.

net/ethtool/cabletest.c
   307  int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info)
   308  {
   309          struct ethnl_req_info req_info = {};
   310          const struct ethtool_phy_ops *ops;
   311          struct nlattr **tb = info->attrs;
   312          struct phy_device *phydev;
   313          struct phy_tdr_config cfg;
   314          struct net_device *dev;
   315          int ret;
   316  
   317          ret = ethnl_parse_header_dev_get(&req_info,
   318                                           tb[ETHTOOL_A_CABLE_TEST_TDR_HEADER],
   319                                           genl_info_net(info), info->extack,
   320                                           true);
   321          if (ret < 0)
   322                  return ret;
   323  
   324          dev = req_info.dev;
   325  
   326          ret = ethnl_act_cable_test_tdr_cfg(tb[ETHTOOL_A_CABLE_TEST_TDR_CFG],
   327                                             info, &cfg);
   328          if (ret)
   329                  goto out_dev_put;
   330  
   331          rtnl_lock();
                ^^^^^^^^^^^^

   332          phydev = ethnl_req_get_phydev(&req_info,
   333                                        tb[ETHTOOL_A_CABLE_TEST_TDR_HEADER],
   334                                        info->extack);
   335          if (!IS_ERR_OR_NULL(phydev)) {
                    ^
This test is reversed so it will lead to a crash.

Could you add some comments to ethnl_req_get_phydev() what the NULL return
means vs the error pointers?  I figured it out because the callers have comments
but it should be next to ethnl_req_get_phydev() as well.

   336                  ret = -EOPNOTSUPP;
   337                  goto out_dev_put;
   338          }
   339  
   340          ops = ethtool_phy_ops;
   341          if (!ops || !ops->start_cable_test_tdr) {
   342                  ret = -EOPNOTSUPP;
   343                  goto out_rtnl;
   344          }
   345  
   346          ret = ethnl_ops_begin(dev);
   347          if (ret < 0)
   348                  goto out_rtnl;
   349  
   350          ret = ops->start_cable_test_tdr(phydev, info->extack, &cfg);
   351  
   352          ethnl_ops_complete(dev);
   353  
   354          if (!ret)
   355                  ethnl_cable_test_started(phydev,
   356                                           ETHTOOL_MSG_CABLE_TEST_TDR_NTF);
   357  
   358  out_rtnl:
   359          rtnl_unlock();
   360  out_dev_put:
   361          ethnl_parse_header_dev_put(&req_info);
   362          return ret;
   363  }

regards,
dan carpenter