linux-kernel - Re: [PATCH] can: usb_8dev: fix possible double dev_kfree_skb in usb_8dev_start

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Message-ID: <de416319-c027-837d-4b8c-b8c3c37ed88e@gmail.com>
Date:   Mon, 21 Mar 2022 09:47:58 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     wg@...ndegger.com, mkl@...gutronix.de, davem@...emloft.net,
        kuba@...nel.org, stefan.maetje@....eu, mailhol.vincent@...adoo.fr,
        paskripkin@...il.com, b.krumboeck@...il.com
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] can: usb_8dev: fix possible double dev_kfree_skb in
 usb_8dev_start_xmit

Gentle ping.

On 2022/3/11 16:06, Hangyu Hua wrote:
> There is no need to call dev_kfree_skb when usb_submit_urb fails beacause
> can_put_echo_skb deletes original skb and can_free_echo_skb deletes the cloned
> skb.
> 
> Fixes: 0024d8ad1639 ("can: usb_8dev: Add support for USB2CAN interface from 8 devices")
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---
>   drivers/net/can/usb/usb_8dev.c | 30 ++++++++++++++----------------
>   1 file changed, 14 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/can/usb/usb_8dev.c b/drivers/net/can/usb/usb_8dev.c
> index 431af1ec1e3c..b638604bf1ee 100644
> --- a/drivers/net/can/usb/usb_8dev.c
> +++ b/drivers/net/can/usb/usb_8dev.c
> @@ -663,9 +663,20 @@ static netdev_tx_t usb_8dev_start_xmit(struct sk_buff *skb,
>   	atomic_inc(&priv->active_tx_urbs);
>   
>   	err = usb_submit_urb(urb, GFP_ATOMIC);
> -	if (unlikely(err))
> -		goto failed;
> -	else if (atomic_read(&priv->active_tx_urbs) >= MAX_TX_URBS)
> +	if (unlikely(err)) {
> +		can_free_echo_skb(netdev, context->echo_index, NULL);
> +
> +		usb_unanchor_urb(urb);
> +		usb_free_coherent(priv->udev, size, buf, urb->transfer_dma);
> +
> +		atomic_dec(&priv->active_tx_urbs);
> +
> +		if (err == -ENODEV)
> +			netif_device_detach(netdev);
> +		else
> +			netdev_warn(netdev, "failed tx_urb %d\n", err);
> +		stats->tx_dropped++;
> +	} else if (atomic_read(&priv->active_tx_urbs) >= MAX_TX_URBS)
>   		/* Slow down tx path */
>   		netif_stop_queue(netdev);
>   
> @@ -684,19 +695,6 @@ static netdev_tx_t usb_8dev_start_xmit(struct sk_buff *skb,
>   
>   	return NETDEV_TX_BUSY;
>   
> -failed:
> -	can_free_echo_skb(netdev, context->echo_index, NULL);
> -
> -	usb_unanchor_urb(urb);
> -	usb_free_coherent(priv->udev, size, buf, urb->transfer_dma);
> -
> -	atomic_dec(&priv->active_tx_urbs);
> -
> -	if (err == -ENODEV)
> -		netif_device_detach(netdev);
> -	else
> -		netdev_warn(netdev, "failed tx_urb %d\n", err);
> -
>   nomembuf:
>   	usb_free_urb(urb);
>