Re: [PATCH] appletalk: Fix potential NULL pointer dereference in unregister_snap_client

[David Miller]

From: Yue Haibing <yuehaibing@xxxxxxxxxx>
Date: Tue, 12 Mar 2019 10:04:26 +0800

>  	timer_setup(&aarp_timer, aarp_expire_timeout, 0);
>  	aarp_timer.expires  = jiffies + sysctl_aarp_expiry_time;
>  	add_timer(&aarp_timer);
> -	register_netdevice_notifier(&aarp_notifier);
> +	rc = register_netdevice_notifier(&aarp_notifier);
> +	if (rc)
> +		unregister_snap_client(aarp_dl);
> +	return rc;

You've left the timer running in this error path.