From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next] enic: add sw timestamp support
Date: Sun, 03 Dec 2017 10:16:23 -0500 (EST)
Message-ID: <20171203.101623.172697821779462247.davem@davemloft.net>
References: <20171201182140.4594-1-gvaradar@cisco.com>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: netdev@vger.kernel.org, benve@cisco.com
To: gvaradar@cisco.com
Return-path: <netdev-owner@vger.kernel.org>
Received: from shards.monkeyblade.net ([184.105.139.130]:36282 "EHLO
        shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751989AbdLCPQZ (ORCPT
        <rfc822;netdev@vger.kernel.org>); Sun, 3 Dec 2017 10:16:25 -0500
In-Reply-To: <20171201182140.4594-1-gvaradar@cisco.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

From: Govindarajulu Varadarajan <gvaradar@cisco.com>
Date: Fri,  1 Dec 2017 10:21:40 -0800

> Add ethtool ops to advertise sw timestamping.
> Call skb_tx_timestamp() just before ringing the wq doorbell.
> 
> Signed-off-by: Govindarajulu Varadarajan <gvaradar@cisco.com>
...
> diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c b/drivers/net/ethernet/cisco/enic/enic_main.c
> index e130fb757e7b..d98676e43e03 100644
> --- a/drivers/net/ethernet/cisco/enic/enic_main.c
> +++ b/drivers/net/ethernet/cisco/enic/enic_main.c
> @@ -856,6 +856,7 @@ static netdev_tx_t enic_hard_start_xmit(struct sk_buff *skb,
>  
>  	if (vnic_wq_desc_avail(wq) < MAX_SKB_FRAGS + ENIC_DESC_MAX_SPLITS)
>  		netif_tx_stop_queue(txq);
> +	skb_tx_timestamp(skb);
>  	if (!skb->xmit_more || netif_xmit_stopped(txq))
>  		vnic_wq_doorbell(wq);
>  

Applied, but if you even make this queue processing code lockless you will
have a use-after-free here as you're placing the SKB into the TX queue
before accessing the 'skb' via skb_tx_timestamp() and it thus could be
freed by TX completion beforehand.