2022-03-11 23:04:43

by Hangyu Hua

Subject: [PATCH] can: usb_8dev: fix possible double dev_kfree_skb in usb_8dev_start_xmit

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 <[email protected]>
---
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);

--
2.25.1

2022-03-21 18:29:46

by Hangyu Hua

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 <[email protected]>
> ---
> 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);
>