Re: [PATCH] net: core: Fix possible null-pointer dereference in failover_slave_register()

[Jakub Kicinski]

On Tue, 10 Aug 2021 02:18:00 -0700 Tuo Li wrote:
> The variable fops is checked in:
>   if (fops && fops->slave_pre_register &&
>     fops->slave_pre_register(slave_dev, failover_dev))
> 
> This indicates that it can be NULL.
> However, it is dereferenced when calling netdev_rx_handler_register():
>   err = netdev_rx_handler_register(slave_dev, fops->slave_handle_frame,
>                     failover_dev);
> 
> To fix this possible null-pointer dereference, check fops first, and if 
> it is NULL, assign -EINVAL to err.

The other fops checks look like defensive programming. I don't see
anywhere where fops would be cleared, and all callers pass it to
register().