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

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hello Dan,

On Tue, 27 Aug 2024 11:27:48 +0300
Dan Carpenter <dan.carpenter@linaro.org> wrote:

> 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.

Good catch ! I'll send some followup to address this report as
well as update the doc.

Thanks,

Maxime