netdev - Re: [RFC] macvlan: add tap device backend

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Date:	Mon, 14 Dec 2009 13:53:14 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Stephen Hemminger <shemminger@...ux-foundation.org>,
	"" <davem@...emloft.net>, "Michael S. Tsirkin" <mst@...hat.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Or Gerlitz <ogerlitz@...taire.com>,
	"Fischer, Anna" <anna.fischer@...com>,
	Anthony Liguori <anthony@...emonkey.ws>,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	bridge@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Edge Virtual Bridging <evb@...oogroups.com>
Subject: Re: [RFC] macvlan: add tap device backend

Arnd Bergmann wrote:
> +static int macvtap_newlink(struct net *src_net,
> +			   struct net_device *dev,
> +			   struct nlattr *tb[],
> +			   struct nlattr *data[])
> +{
> +	struct device *classdev;
> +	dev_t devt;
> +	int err;
> +
> +	err = macvlan_common_newlink(src_net, dev, tb, data,
> +				     macvtap_receive, macvtap_forward);
> +	if (err)
> +		goto out;
> +
> +	devt = MKDEV(MAJOR(macvtap_major), dev->ifindex);
> +
> +	classdev = device_create(macvtap_class, &dev->dev, devt,
> +				 dev, "tap%d", dev->ifindex);
> +	if (IS_ERR(classdev)) {
> +		err = PTR_ERR(classdev);
> +		macvtap_del_queues(dev);
> +		macvlan_dellink(dev, NULL);

I think this may cause a double free since macvlan_dellink() will
free the device and rtnl_newlink() will free it again on error.

> +	}
> +
> +out:
> +	return err;
> +}
> +
> +static void macvtap_dellink(struct net_device *dev,
> +			    struct list_head *head)
> +{
> +	device_destroy(macvtap_class,
> +		       MKDEV(MAJOR(macvtap_major), dev->ifindex));
> +
> +	macvtap_del_queues(dev);
> +	macvlan_dellink(dev, head);
> +}
> +
> +static struct rtnl_link_ops macvtap_link_ops __read_mostly = {
> +	.kind		= "macvtap",
> +	.newlink	= macvtap_newlink,
> +	.dellink	= macvtap_dellink,
> +};
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