netdev - Re: [PATCH net] sfc: fix potential memleak in __ef100_hard_start

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Date:   Fri, 18 Nov 2022 19:53:51 +0800
From:   Zhang Changzhong <zhangchangzhong@...wei.com>
To:     Leon Romanovsky <leon@...nel.org>,
        Edward Cree <ecree.xilinx@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] sfc: fix potential memleak in
 __ef100_hard_start_xmit()

On 2022/11/18 17:15, Martin Habets wrote:
> On Thu, Nov 17, 2022 at 03:05:27PM +0200, Leon Romanovsky wrote:
>> On Thu, Nov 17, 2022 at 08:41:52PM +0800, Zhang Changzhong wrote:
>>>
>>>
>>> On 2022/11/17 19:36, Leon Romanovsky wrote:
>>>> On Thu, Nov 17, 2022 at 03:50:09PM +0800, Zhang Changzhong wrote:
>>>>> The __ef100_hard_start_xmit() returns NETDEV_TX_OK without freeing skb
>>>>> in error handling case, add dev_kfree_skb_any() to fix it.
>>>>>
>>>>> Fixes: 51b35a454efd ("sfc: skeleton EF100 PF driver")
>>>>> Signed-off-by: Zhang Changzhong <zhangchangzhong@...wei.com>
>>>>> ---
>>>>>  drivers/net/ethernet/sfc/ef100_netdev.c | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/drivers/net/ethernet/sfc/ef100_netdev.c b/drivers/net/ethernet/sfc/ef100_netdev.c
>>>>> index 88fa295..ddcc325 100644
>>>>> --- a/drivers/net/ethernet/sfc/ef100_netdev.c
>>>>> +++ b/drivers/net/ethernet/sfc/ef100_netdev.c
>>>>> @@ -218,6 +218,7 @@ netdev_tx_t __ef100_hard_start_xmit(struct sk_buff *skb,
>>>>>  		   skb->len, skb->data_len, channel->channel);
>>>>>  	if (!efx->n_channels || !efx->n_tx_channels || !channel) {
>>>>>  		netif_stop_queue(net_dev);
>>>>> +		dev_kfree_skb_any(skb);
>>>>>  		goto err;
>>>>>  	}
>>>>
>>>> ef100 doesn't release in __ef100_enqueue_skb() either. SKB shouldn't be
>>>> NULL or ERR at this stage.
>>>
>>> SKB shouldn't be NULL or ERR, so it can be freed. But this code looks weird.
>>
>> Please take a look __ef100_enqueue_skb() and see if it frees SKB on
>> error or not. If not, please fix it.
> 
> That function looks ok to me, but I appreciate the extra eyes on it.
> 

I've looked at this function and it seems every error handling path frees the skb.

Thanks,
Changzhong


> Martin
> 
>> Thanks
>>
>>>
>>>>
>>>> diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
>>>> index 29ffaf35559d..426706b91d02 100644
>>>> --- a/drivers/net/ethernet/sfc/ef100_tx.c
>>>> +++ b/drivers/net/ethernet/sfc/ef100_tx.c
>>>> @@ -497,7 +497,7 @@ int __ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
>>>>
>>>>  err:
>>>>         efx_enqueue_unwind(tx_queue, old_insert_count);
>>>> -       if (!IS_ERR_OR_NULL(skb))
>>>> +       if (rc)
>>>>                 dev_kfree_skb_any(skb);
>>>>
>>>>         /* If we're not expecting another transmit and we had something to push
>>>>
>>>>
>>>>>  
>>>>> -- 
>>>>> 2.9.5
>>>>>
>>>> .
>>>>
> .
>