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Date: Sat, 19 Dec 2015 15:06:45 +0300 From: Alexey Khoroshilov <khoroshilov@...ras.ru> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org Subject: Re: [PATCH] natsemi: add checks for dma mapping errors On 19.12.2015 05:36, David Miller wrote: > 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. I do not quite understand what do you mean by 'freeing the SKB'. At least the patch left skb untouched. But I saw such pattern, for example, in drivers/net/ethernet/freescale/fec_main.c: addr = dma_map_single(&fep->pdev->dev, data, size, DMA_TO_DEVICE); if (dma_mapping_error(&fep->pdev->dev, addr)) { dev_kfree_skb_any(skb); if (net_ratelimit()) netdev_err(ndev, "Tx DMA memory map failed\n"); return NETDEV_TX_BUSY; } > > NETDEV_TX_BUSY is only for buggy drivers that do not manage their > TX ring busy condition correctly, and thus need retries. Ok, I will replace NETDEV_TX_BUSY by dropping the packet. -- Alexey -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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