netdev - Re: [RFC PATCH 5/5] geneve: add initial netdev driver for GENEVE tunnels

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Date:	Fri, 3 Apr 2015 14:55:02 +0900
From:	Simon Horman <simon.horman@...ronome.com>
To:	"John W. Linville" <linville@...driver.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Jesse Gross <jesse@...ira.com>, Andy Zhou <azhou@...ira.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Alexander Duyck <alexander.h.duyck@...hat.com>
Subject: Re: [RFC PATCH 5/5] geneve: add initial netdev driver for GENEVE
 tunnels

Hi John,

On Thu, Apr 02, 2015 at 03:17:06PM -0400, John W. Linville wrote:
> This is an initial implementation of a netdev driver for GENEVE
> tunnels.  This implementation uses a fixed UDP port, and only supports
> a single tunnel (and therefore only a single VNI) per net namespace.
> Only IPv4 links are supported at this time.
> 
> Signed-off-by: John W. Linville <linville@...driver.com>

Thanks for working on this. I'm very happy to see a Geneve driver hit netdev.

I have a question below.

[snip]

> +/* Scheduled at device creation to bind to a socket */
> +static void geneve_sock_work(struct work_struct *work)
> +{
> +	struct geneve_dev *geneve = container_of(work, struct geneve_dev, sock_work);
> +	struct net *net = geneve->net;
> +	struct geneve_sock *gs;
> +
> +	gs = geneve_sock_add(net, htons(GENEVE_UDP_PORT), geneve_rx, geneve,
> +	                     true, false);
> +	if (!IS_ERR(gs))
> +		geneve->sock = gs;
> +
> +	dev_put(geneve->dev);
> +}
> +
> +/* Setup stats when device is created */
> +static int geneve_init(struct net_device *dev)
> +{
> +	struct geneve_dev *geneve = netdev_priv(dev);
> +
> +	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
> +	if (!dev->tstats)
> +		return -ENOMEM;
> +
> +	/* make new socket outside of RTNL */
> +	dev_hold(dev);
> +	queue_work(geneve_wq, &geneve->sock_work);
> +
> +	return 0;
> +}
> +
> +static void geneve_uninit(struct net_device *dev)
> +{
> +	struct geneve_dev *geneve = netdev_priv(dev);
> +	struct geneve_sock *gs = geneve->sock;
> +
> +	if (gs)
> +		geneve_sock_release(gs);
> +	free_percpu(dev->tstats);
> +}

I am wondering if there a possibility that geneve_sock_work() could run
after the check for gs in geneve_uninit() thus leaking gs?

[snip]
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