netdev - Re: [PATCH 4/5] net: wwan: iosm: fix netdev tx stats

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Date:   Wed, 30 Jun 2021 22:36:50 +0200
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     M Chetan Kumar <m.chetan.kumar@...ux.intel.com>,
        netdev@...r.kernel.org
Cc:     kuba@...nel.org, davem@...emloft.net, johannes@...solutions.net,
        krishna.c.sudi@...el.com, linuxwwan@...el.com
Subject: Re: [PATCH 4/5] net: wwan: iosm: fix netdev tx stats



On 6/30/21 8:27 PM, M Chetan Kumar wrote:
> Update tx stats on successful packet consume, drop.
> 
> Signed-off-by: M Chetan Kumar <m.chetan.kumar@...ux.intel.com>
> ---
>  drivers/net/wwan/iosm/iosm_ipc_wwan.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wwan/iosm/iosm_ipc_wwan.c b/drivers/net/wwan/iosm/iosm_ipc_wwan.c
> index 84e37c4b0f74..561944a33725 100644
> --- a/drivers/net/wwan/iosm/iosm_ipc_wwan.c
> +++ b/drivers/net/wwan/iosm/iosm_ipc_wwan.c
> @@ -123,6 +123,8 @@ static int ipc_wwan_link_transmit(struct sk_buff *skb,
>  
>  	/* Return code of zero is success */
>  	if (ret == 0) {
> +		netdev->stats.tx_packets++;
> +		netdev->stats.tx_bytes += skb->len;

What makes you think skb has not been consumed already ?
It seems clear it has been given, this thread can not expect skb has not been mangled/freed.
skb->len might now contain garbage, or even crash the kernel under appropriate debug features.

>  		ret = NETDEV_TX_OK;
>  	} else if (ret == -EBUSY) {
>  		ret = NETDEV_TX_BUSY;
> @@ -140,7 +142,8 @@ static int ipc_wwan_link_transmit(struct sk_buff *skb,
>  			ret);
>  
>  	dev_kfree_skb_any(skb);
> -	return ret;
> +	netdev->stats.tx_dropped++;
> +	return NETDEV_TX_OK;
>  }
>  
>  /* Ops structure for wwan net link */
>