linux-kernel - Re: Deadlock, L2TP over IP are not working, 3.4.1

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 07 Jun 2012 23:30:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	Denys Fedoryshchenko <denys@...p.net.lb>, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Deadlock, L2TP over IP are not working, 3.4.1

On Thu, 2012-06-07 at 22:53 +0200, Francois Romieu wrote:

> Any reason why it could not be made LLTX ?
> 

>  /* via l2tp_session_priv() */
> @@ -87,25 +95,56 @@ static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
>  {
>  	struct l2tp_eth *priv = netdev_priv(dev);
>  	struct l2tp_session *session = priv->session;
> +	struct l2tp_eth_stats *tstats = &priv->tstats;
>  
>  	l2tp_xmit_skb(session, skb, session->hdr_len);
>  
> -	dev->stats.tx_bytes += skb->len;
> -	dev->stats.tx_packets++;
> +	u64_stats_update_begin(&tstats->syncp);
> +	tstats->packets++;
> +	tstats->bytes += skb->len;
> +	u64_stats_update_end(&tstats->syncp);
>  
>  	return 0;
>  }
>  

Its racy.

If LLTX is used, this means several cpus can execute this code at the
same time.

You need percpu stats, or use atomic primitives.



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/