netdev - Re: [PATCH net] net: nixge: fix potential memory leak in nixge_start

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Date:   Tue, 15 Nov 2022 21:20:44 +0800
From:   Zhang Changzhong <zhangchangzhong@...wei.com>
To:     Francois Romieu <romieu@...zoreil.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Moritz Fischer <mdf@...nel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: nixge: fix potential memory leak in
 nixge_start_xmit()

On 2022/11/14 18:40, Francois Romieu wrote:
> Zhang Changzhong <zhangchangzhong@...wei.com> :
>> The nixge_start_xmit() returns NETDEV_TX_OK but does not free skb on two
>> error handling cases, which can lead to memory leak.
>>
>> To fix this, return NETDEV_TX_BUSY in case of nixge_check_tx_bd_space()
>> fails and add dev_kfree_skb_any() in case of dma_map_single() fails.
> 
> This patch merge two unrelated changes. Please split.
> 
>> Fixes: 492caffa8a1a ("net: ethernet: nixge: Add support for National Instruments XGE netdev")
>> Signed-off-by: Zhang Changzhong <zhangchangzhong@...wei.com>
>> ---
>>  drivers/net/ethernet/ni/nixge.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c
>> index 19d043b593cc..b9091f9bbc77 100644
>> --- a/drivers/net/ethernet/ni/nixge.c
>> +++ b/drivers/net/ethernet/ni/nixge.c
>> @@ -521,13 +521,15 @@ static netdev_tx_t nixge_start_xmit(struct sk_buff *skb,
>>  	if (nixge_check_tx_bd_space(priv, num_frag)) {
>>  		if (!netif_queue_stopped(ndev))
>>  			netif_stop_queue(ndev);
>> -		return NETDEV_TX_OK;
>> +		return NETDEV_TX_BUSY;
>>  	}
> 
> The driver should probably check the available room before returning
> from hard_start_xmit and turn the check above unlikely().
> 
> Btw there is no lock and the Tx completion is irq driven: the driver
> is racy. :o(
> 

Hi Francois,

Thanks for you review. I'll make v2 according to your suggestion.

Changzhong