netdev - Re: [PATCH v2 1/2] net: macb: Check DMA mappings for error

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Date:	Thu, 27 Feb 2014 23:57:39 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Soren Brinkmann <soren.brinkmann@...inx.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Michal Simek <michal.simek@...inx.com>
Subject: Re: [PATCH v2 1/2] net: macb: Check DMA mappings for error

On Thu, 2014-02-27 at 13:58 -0800, Soren Brinkmann wrote:
[...]
> diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> index 3190d38e16fb..a9c2ccfc1740 100644
> --- a/drivers/net/ethernet/cadence/macb.c
> +++ b/drivers/net/ethernet/cadence/macb.c
> @@ -632,11 +632,16 @@ static void gem_rx_refill(struct macb *bp)
>  					   "Unable to allocate sk_buff\n");
>  				break;
>  			}
> -			bp->rx_skbuff[entry] = skb;
>  
>  			/* now fill corresponding descriptor entry */
>  			paddr = dma_map_single(&bp->pdev->dev, skb->data,
>  					       bp->rx_buffer_size, DMA_FROM_DEVICE);
> +			if (dma_mapping_error(&bp->pdev->dev, paddr)) {
> +				dev_kfree_skb(skb);
> +				break;
> +			}
> +
> +			bp->rx_skbuff[entry] = skb;
>  
>  			if (entry == RX_RING_SIZE - 1)
>  				paddr |= MACB_BIT(RX_WRAP);
> @@ -1040,6 +1045,10 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)

A bit more context:

	entry = macb_tx_ring_wrap(bp->tx_head);
	bp->tx_head++;

>  	netdev_vdbg(bp->dev, "Allocated ring entry %u\n", entry);
>  	mapping = dma_map_single(&bp->pdev->dev, skb->data,
>  				 len, DMA_TO_DEVICE);
> +	if (dma_mapping_error(&bp->pdev->dev, mapping)) {
> +		kfree_skb(skb);
> +		goto unlock;
> +	}

You need to move the bp->tx_head increment below this error check.
Sorry I didn't spot this the first time.

Ben.

>  	tx_skb = &bp->tx_skb[entry];
>  	tx_skb->skb = skb;
> @@ -1066,6 +1075,7 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	if (CIRC_SPACE(bp->tx_head, bp->tx_tail, TX_RING_SIZE) < 1)
>  		netif_stop_queue(dev);
>  
> +unlock:
>  	spin_unlock_irqrestore(&bp->lock, flags);
>  
>  	return NETDEV_TX_OK;

-- 
Ben Hutchings
It is easier to change the specification to fit the program than vice versa.

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