netdev - Re: [PATCH] forcedeth: Fix WARNINGS that result when DMA mapping is not checked

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Date:	Thu, 27 Dec 2012 12:05:15 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	linville@...driver.com, davem@...emloft.net,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] forcedeth: Fix WARNINGS that result when DMA mapping
 is not checked

On Thu, 2012-12-27 at 13:42 -0600, Larry Finger wrote:
> With 3.8-rc1, the first call of pci_map_single() that is not checked
> with a corresponding pci_dma_mapping_error() call results in a warning
> with a splat as follows:
> 
> WARNING: at lib/dma-debug.c:933 check_unmap+0x480/0x950()
> Hardware name: HP Pavilion dv2700 Notebook PC
> forcedeth 0000:00:0a.0: DMA-API: device driver failed to check
>  map error[device address=0x00000000b176e002] [size=90 bytes] [mapped as single]
> 
> Signed-off-by: Larry Finger <Larry.Finger@...inger.net>
> ---
>  drivers/net/ethernet/nvidia/forcedeth.c |   23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/net/ethernet/nvidia/forcedeth.c b/drivers/net/ethernet/nvidia/forcedeth.c
> index 653487d..de39cf2 100644
> --- a/drivers/net/ethernet/nvidia/forcedeth.c
> +++ b/drivers/net/ethernet/nvidia/forcedeth.c
> @@ -1821,6 +1821,11 @@ static int nv_alloc_rx(struct net_device *dev)
>  							     skb->data,
>  							     skb_tailroom(skb),
>  							     PCI_DMA_FROMDEVICE);
> +			if (pci_dma_mapping_error(np->pci_dev,
> +						  np->put_rx_ctx->dma)) {
> +				dev_kfree_skb_any(skb);

skb has no destructor yet, kfree_skb(skb) should be fine

> +				goto packet_dropped;
> +			}
>  			np->put_rx_ctx->dma_len = skb_tailroom(skb);
>  			np->put_rx.orig->buf = cpu_to_le32(np->put_rx_ctx->dma);
>  			wmb();
> @@ -1830,6 +1835,7 @@ static int nv_alloc_rx(struct net_device *dev)
>  			if (unlikely(np->put_rx_ctx++ == np->last_rx_ctx))
>  				np->put_rx_ctx = np->first_rx_ctx;
>  		} else {
> +packet_dropped:
>  			u64_stats_update_begin(&np->swstats_rx_syncp);
>  			np->stat_rx_dropped++;
>  			u64_stats_update_end(&np->swstats_rx_syncp);
> @@ -1856,6 +1862,11 @@ static int nv_alloc_rx_optimized(struct net_device *dev)
>  							     skb->data,
>  							     skb_tailroom(skb),
>  							     PCI_DMA_FROMDEVICE);
> +			if (pci_dma_mapping_error(np->pci_dev,
> +						  np->put_rx_ctx->dma)) {
> +				dev_kfree_skb_any(skb);
> +				goto packet_dropped;
> +			}
>  			np->put_rx_ctx->dma_len = skb_tailroom(skb);
>  			np->put_rx.ex->bufhigh = cpu_to_le32(dma_high(np->put_rx_ctx->dma));
>  			np->put_rx.ex->buflow = cpu_to_le32(dma_low(np->put_rx_ctx->dma));
> @@ -1866,6 +1877,7 @@ static int nv_alloc_rx_optimized(struct net_device *dev)
>  			if (unlikely(np->put_rx_ctx++ == np->last_rx_ctx))
>  				np->put_rx_ctx = np->first_rx_ctx;
>  		} else {
> +packet_dropped:
>  			u64_stats_update_begin(&np->swstats_rx_syncp);
>  			np->stat_rx_dropped++;
>  			u64_stats_update_end(&np->swstats_rx_syncp);
> @@ -2217,6 +2229,9 @@ static netdev_tx_t nv_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  		bcnt = (size > NV_TX2_TSO_MAX_SIZE) ? NV_TX2_TSO_MAX_SIZE : size;
>  		np->put_tx_ctx->dma = pci_map_single(np->pci_dev, skb->data + offset, bcnt,
>  						PCI_DMA_TODEVICE);
> +		if (pci_dma_mapping_error(np->pci_dev,
> +					  np->put_tx_ctx->dma))
> +			return NETDEV_TX_BUSY;

Really this is not going to work very well : caller will call this in a
loop.

>  		np->put_tx_ctx->dma_len = bcnt;
>  		np->put_tx_ctx->dma_single = 1;
>  		put_tx->buf = cpu_to_le32(np->put_tx_ctx->dma);
> @@ -2337,6 +2352,9 @@ static netdev_tx_t nv_start_xmit_optimized(struct sk_buff *skb,
>  		bcnt = (size > NV_TX2_TSO_MAX_SIZE) ? NV_TX2_TSO_MAX_SIZE : size;
>  		np->put_tx_ctx->dma = pci_map_single(np->pci_dev, skb->data + offset, bcnt,
>  						PCI_DMA_TODEVICE);
> +		if (pci_dma_mapping_error(np->pci_dev,
> +					  np->put_tx_ctx->dma))
> +			return NETDEV_TX_BUSY;

same problem here.

>  		np->put_tx_ctx->dma_len = bcnt;
>  		np->put_tx_ctx->dma_single = 1;
>  		put_tx->bufhigh = cpu_to_le32(dma_high(np->put_tx_ctx->dma));
> @@ -5003,6 +5021,11 @@ static int nv_loopback_test(struct net_device *dev)
>  	test_dma_addr = pci_map_single(np->pci_dev, tx_skb->data,
>  				       skb_tailroom(tx_skb),
>  				       PCI_DMA_FROMDEVICE);
> +	if (pci_dma_mapping_error(np->pci_dev,
> +				  test_dma_addr)) {
> +		dev_kfree_skb_any(tx_skb);

		kfree_skb(skb);

> +		goto out;
> +	}
>  	pkt_data = skb_put(tx_skb, pkt_len);
>  	for (i = 0; i < pkt_len; i++)
>  		pkt_data[i] = (u8)(i & 0xff);


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