netdev - Re: [PATCH net-next] macvtap: check minor when unregistering

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Date:	Mon, 25 Apr 2016 14:01:06 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Francesco Ruggeri <fruggeri@...sta.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next] macvtap: check minor when unregistering

Francesco Ruggeri <fruggeri@...sta.com> writes:

> macvtap_device_event(NETDEV_UNREGISTER) should check vlan->minor to
> determine if it is being invoked in the context of a macvtap_newlink
> that failed, for example in this code sequence:
>
> macvtap_newlink
>   macvlan_common_newlink
>     register_netdevice
>       call_netdevice_notifiers(NETDEV_REGISTER, dev)
>         macvtap_device_event(NETDEV_REGISTER)
>           <fail here, vlan->minor = 0>
>       rollback_registered(dev);
>         rollback_registered_many
>           call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
>             macvtap_device_event(NETDEV_UNREGISTER)
>               <nothing to clean up here>
>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com>
> ---
>  drivers/net/macvtap.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 95394ed..74cb15a 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -1303,6 +1303,9 @@ static int macvtap_device_event(struct notifier_block *unused,
>  		}
>  		break;
>  	case NETDEV_UNREGISTER:
> +		/* vlan->minor == 0 if NETDEV_REGISTER above failed */
> +		if (vlan->minor == 0)
> +			break;
>  		devt = MKDEV(MAJOR(macvtap_major), vlan->minor);
>  		device_destroy(macvtap_class, devt);
>  		macvtap_free_minor(vlan);