netdev - Re: rcu locking issue in mpls output code?

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Message-ID: <8d325ab7-bc46-dd69-288a-571d56efc545@cumulusnetworks.com>
Date:	Sun, 19 Jun 2016 20:19:20 -0600
From:	David Ahern <dsa@...ulusnetworks.com>
To:	Lennert Buytenhek <buytenh@...tstofly.org>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	Robert Shearman <rshearma@...cade.com>
Cc:	netdev@...r.kernel.org
Subject: Re: rcu locking issue in mpls output code?

On 6/19/16 6:45 PM, Lennert Buytenhek wrote:
> diff --git a/net/mpls/mpls_iptunnel.c b/net/mpls/mpls_iptunnel.c
> index fb31aa8..802956b 100644
> --- a/net/mpls/mpls_iptunnel.c
> +++ b/net/mpls/mpls_iptunnel.c
> @@ -105,12 +105,15 @@ static int mpls_output(struct net *net, struct sock *sk, struct sk_buff *skb)
>  		bos = false;
>  	}
>
> +	rcu_read_lock_bh();
>  	if (rt)
>  		err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gateway,
>  				 skb);
>  	else if (rt6)
>  		err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
>  				 skb);
> +	rcu_read_unlock_bh();
> +
>  	if (err)
>  		net_dbg_ratelimited("%s: packet transmission failed: %d\n",
>  				    __func__, err);
>

I think those need to be added to neigh_xmit in the

	if (likely(index < NEIGH_NR_TABLES)) {

	}

block.