Re: [PATCH] ipheth: fix EOVERFLOW in ipheth_rcvbulk_callback

[Jakub Kicinski]

On Mon, 31 Jan 2022 19:58:14 +0100 Jan Kiszka wrote:
> From: Georgi Valkov <gvalkov@xxxxxx>
> 
> When rx_buf is allocated we need to account for IPHETH_IP_ALIGN,
> which reduces the usable size by 2 bytes. Otherwise we have 1512
> bytes usable instead of 1514, and if we receive more than 1512
> bytes, ipheth_rcvbulk_callback is called with status -EOVERFLOW,
> after which the driver malfunctiones and all communication stops.
> 
> Resolves ipheth 2-1:4.2: ipheth_rcvbulk_callback: urb status: -75
> 
> Fixes: f33d9e2b48a3 ("usbnet: ipheth: fix connectivity with iOS 14")
> Signed-off-by: Georgi Valkov <gvalkov@xxxxxx>
> Tested-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

Hm, I'm starting to suspect this patch is cursed..

> diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c
> index cd33955df0b6..6a769df0b421 100644
> --- a/drivers/net/usb/ipheth.c
> +++ b/drivers/net/usb/ipheth.c
> @@ -121,7 +121,7 @@ static int ipheth_alloc_urbs(struct ipheth_device *iphone)
>   	if (tx_buf == NULL)

There is an extra space character at the start of each line of context.

>   		goto free_rx_urb;
>   
> -	rx_buf = usb_alloc_coherent(iphone->udev, IPHETH_BUF_SIZE,

But not on the changed lines.

> +	rx_buf = usb_alloc_coherent(iphone->udev, IPHETH_BUF_SIZE + IPHETH_IP_ALIGN,
>   				    GFP_KERNEL, &rx_urb->transfer_dma);
>   	if (rx_buf == NULL)
>   		goto free_tx_buf;
> @@ -146,7 +146,7 @@ static int ipheth_alloc_urbs(struct ipheth_device *iphone)
>   
>   static void ipheth_free_urbs(struct ipheth_device *iphone)
>   {
> -	usb_free_coherent(iphone->udev, IPHETH_BUF_SIZE, iphone->rx_buf,

Pretty clear here in how the opening bracket does not align after the -.

> +	usb_free_coherent(iphone->udev, IPHETH_BUF_SIZE + IPHETH_IP_ALIGN, iphone->rx_buf,
>   			  iphone->rx_urb->transfer_dma);
>   	usb_free_coherent(iphone->udev, IPHETH_BUF_SIZE, iphone->tx_buf,
>   			  iphone->tx_urb->transfer_dma);
> @@ -317,7 +317,7 @@ static int ipheth_rx_submit(struct ipheth_device *dev, gfp_t mem_flags)
>   
>   	usb_fill_bulk_urb(dev->rx_urb, udev,
>   			  usb_rcvbulkpipe(udev, dev->bulk_in),
> -			  dev->rx_buf, IPHETH_BUF_SIZE,
> +			  dev->rx_buf, IPHETH_BUF_SIZE + IPHETH_IP_ALIGN,
>   			  ipheth_rcvbulk_callback,
>   			  dev);
>   	dev->rx_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;