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Message-ID: <69b0dd44-93ac-fa33-f9c1-6f787185ab47@gmail.com>
Date:   Mon, 28 Feb 2022 10:05:03 +0800
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Subject: Re: [PATCH] can: usb: fix a possible memory leak in
 esd_usb2_start_xmit
Content-Language: en-US
To:     Marc Kleine-Budde <mkl@pengutronix.de>
Cc:     wg@grandegger.com, davem@davemloft.net, kuba@kernel.org,
        stefan.maetje@esd.eu, mailhol.vincent@wanadoo.fr,
        paskripkin@gmail.com, thunder.leizhen@huawei.com,
        linux-can@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220225060019.21220-1-hbh25y@gmail.com>
 <20220225155621.7zmfukra63qcxjo5@pengutronix.de>
From:   Hangyu Hua <hbh25y@gmail.com>
In-Reply-To: <20220225155621.7zmfukra63qcxjo5@pengutronix.de>
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Hi

I get it. But this means ems_usb_start_xmit have a redundant 
dev_kfree_skb beacause can_put_echo_skb delete original skb and 
can_free_echo_skb delete the cloned skb. While this code is harmless do 
you think we need to delete it ?

Thanks.

On 2022/2/25 23:56, Marc Kleine-Budde wrote:
> On 25.02.2022 14:00:19, Hangyu Hua wrote:
>> As in case of ems_usb_start_xmit, dev_kfree_skb needs to be called when
>> usb_submit_urb fails to avoid possible refcount leaks.
> 
> Thanks for your patch. Have you tested that there is actually a mem
> leak? Please have a look at the can_free_echo_skb() function that is
> called a few lines earlier.
> 
>> Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
>> ---
>>   drivers/net/can/usb/esd_usb2.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/can/usb/esd_usb2.c b/drivers/net/can/usb/esd_usb2.c
>> index 286daaaea0b8..7b5e6c250d00 100644
>> --- a/drivers/net/can/usb/esd_usb2.c
>> +++ b/drivers/net/can/usb/esd_usb2.c
>> @@ -810,7 +810,7 @@ static netdev_tx_t esd_usb2_start_xmit(struct sk_buff *skb,
>>   		usb_unanchor_urb(urb);
>>   
>>   		stats->tx_dropped++;
>> -
>> +		dev_kfree_skb(skb);
>>   		if (err == -ENODEV)
>>   			netif_device_detach(netdev);
>>   		else
> 
> regards,
> Marc
>