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

Hi Pavel,

Thanks for the patch!

On Mon. 15 Nov 2021 at 05:58, Pavel Skripkin [off-list ref] 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")

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

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;
 }