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

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Message-ID: <98a85462-85ca-d289-854d-aa7b11614fae@intel.com>
Date:   Thu, 1 Jul 2021 11:00:13 +0530
From:   "Kumar, M Chetan" <m.chetan.kumar@...el.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        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 7/1/2021 2:06 AM, Eric Dumazet wrote:
> 
> 
> 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.

Ya. there could be a possibility skb might have been dequeued from ul_list and
UL task is already processing it. We can't rule out.

Will backup skb->len to local var and use it for tx_bytes update.

Regards,
Chetan