netdev - Re: [PATCH] can: etas_es58x: fix error handling

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Date:   Mon, 15 Nov 2021 10:40:22 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc:     wg@...ndegger.com, mkl@...gutronix.de, davem@...emloft.net,
        kuba@...nel.org, linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] can: etas_es58x: fix error handling

On 11/15/21 08:27, Vincent MAILHOL wrote:
> Hi Pavel,
> 
> Thanks for the patch!
> 
> On Mon. 15 Nov 2021 at 05:58, Pavel Skripkin <paskripkin@...il.com> wrote:
>> When register_candev() fails there are 2 possible device states:
>> NETREG_UNINITIALIZED and NETREG_UNREGISTERED. None of them are suitable
>> for calling unregister_candev(), because of following checks in
>> unregister_netdevice_many():
>>
>>         if (dev->reg_state == NETREG_UNINITIALIZED)
>>                 WARN_ON(1);
>> ...
>>         BUG_ON(dev->reg_state != NETREG_REGISTERED);
>>
>> To avoid possible BUG_ON or WARN_ON let's free current netdev before
>> returning from es58x_init_netdev() and leave others (registered)
>> net devices for es58x_free_netdevs().
>>
>> Fixes: 004653f0abf2 ("can: etas_es58x: add es58x_free_netdevs() to factorize code")
> 

Hi, Vincent!

> Fixes: 8537257874e9 ("can: etas_es58x: add core support for ETAS ES58X
> CAN USB interfaces")
> 
> The bug existed from the initial commit.  Prior to the
> introduction of es58x_free_netdevs(), unregister_candev() was
> called in the error handling of es58x_probe():
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/can/usb/etas_es58x/es58x_core.c?id=8537257874e949a59c834cecfd5a063e11b64b0b#n2234
> 

I see, will fix in v2

>> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
>> ---
>>  drivers/net/can/usb/etas_es58x/es58x_core.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.c b/drivers/net/can/usb/etas_es58x/es58x_core.c
>> index 96a13c770e4a..41c721f2fbbe 100644
>> --- a/drivers/net/can/usb/etas_es58x/es58x_core.c
>> +++ b/drivers/net/can/usb/etas_es58x/es58x_core.c
>> @@ -2098,8 +2098,11 @@ static int es58x_init_netdev(struct es58x_device *es58x_dev, int channel_idx)
>>         netdev->flags |= IFF_ECHO;      /* We support local echo */
>>
>>         ret = register_candev(netdev);
>> -       if (ret)
>> +       if (ret) {
>> +               free_candev(netdev);
>> +               es58x_dev->netdev[channel_idx] = NULL;
> 
> A nitpick, but if you don’t mind, I would prefer to set
> es58x_dev->netdev[channel_idx] after register_candev() succeeds
> so that we do not have to reset it to NULL in the error handling.
> 
> diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.c
> b/drivers/net/can/usb/etas_es58x/es58x_core.c
> index ce2b9e1ce3af..fb0daad9b9c8 100644
> --- a/drivers/net/can/usb/etas_es58x/es58x_core.c
> +++ b/drivers/net/can/usb/etas_es58x/es58x_core.c
> @@ -2091,18 +2091,20 @@ static int es58x_init_netdev(struct
> es58x_device *es58x_dev, int channel_idx)
>                  return -ENOMEM;
>          }
>          SET_NETDEV_DEV(netdev, dev);
> -       es58x_dev->netdev[channel_idx] = netdev;
>          es58x_init_priv(es58x_dev, es58x_priv(netdev), channel_idx);
> 
>          netdev->netdev_ops = &es58x_netdev_ops;
>          netdev->flags |= IFF_ECHO;      /* We support local echo */
> 
>          ret = register_candev(netdev);
> -       if (ret)
> +       if (ret) {
> +               free_candev(netdev);
>                  return ret;
> +       }
> 
>          netdev_queue_set_dql_min_limit(netdev_get_tx_queue(netdev, 0),
>                                         es58x_dev->param->dql_min_limit);
> +       es58x_dev->netdev[channel_idx] = netdev;
> 
>          return ret;
>   }
> 

Also will do in v2. Thank you for your review :)





With regards,
Pavel Skripkin