netdev - Re: [PATCH] natsemi: add checks for dma mapping errors

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Message-Id: <20151218.213607.1270121670262037282.davem@davemloft.net>
Date:	Fri, 18 Dec 2015 21:36:07 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	khoroshilov@...ras.ru
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org
Subject: Re: [PATCH] natsemi: add checks for dma mapping errors

From: Alexey Khoroshilov <khoroshilov@...ras.ru>
Date: Sat, 19 Dec 2015 00:55:37 +0300

> @@ -2093,6 +2099,10 @@ static netdev_tx_t start_tx(struct sk_buff *skb, struct net_device *dev)
>  	np->tx_skbuff[entry] = skb;
>  	np->tx_dma[entry] = pci_map_single(np->pci_dev,
>  				skb->data,skb->len, PCI_DMA_TODEVICE);
> +	if (pci_dma_mapping_error(np->pci_dev, np->tx_dma[entry])) {
> +		np->tx_skbuff[entry] = NULL;
> +		return NETDEV_TX_BUSY;
> +	}
>  
>  	np->tx_ring[entry].addr = cpu_to_le32(np->tx_dma[entry]);
>  

Returning NETDEV_TX_BUSY and freeing the SKB will crash the system.

NETDEV_TX_BUSY is only for buggy drivers that do not manage their
TX ring busy condition correctly, and thus need retries.
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