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Re: BUG in the PCNET32 ethernet driver

To: Carsten Langgaard <carstenl@mips.com>
Subject: Re: BUG in the PCNET32 ethernet driver
From: Jeff Garzik <jgarzik@pobox.com>
Date: Wed, 13 Nov 2002 15:20:18 -0500
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, tsbogend@alpha.franken.de, linux-net@vger.kernel.org, kevink@mips.com
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Carsten Langgaard wrote:

Jeff Garzik wrote:


>Carsten Langgaard wrote:
>
>
>>@@ -1316,13 +1316,13 @@
>>                  if ((newskb = dev_alloc_skb (PKT_BUF_SZ))) {
>>                      skb_reserve (newskb, 2);
>>                      skb = lp->rx_skbuff[entry];
>>- pci_unmap_single(lp->pci_dev, lp->rx_dma_addr[entry], skb->len,
>>PCI_DMA_FROMDEVICE);
>>+ pci_unmap_single(lp->pci_dev, lp->rx_dma_addr[entry], pkt_len +2,
>>PCI_DMA_FROMDEVICE);
>>                      skb_put (skb, pkt_len);
>>                      lp->rx_skbuff[entry] = newskb;
>
>Why does this line not reference PKT_BUF_SZ when all the others do?


In this case we know the size of the packet and therefore only need to handle that. In the other cases we don't know have big the receiving packet is going to be, so we has to
take care of the whole buffer.



Well, it's a seriously bad idea to pass different values to map and unmap steps, because on some platforms you could wind up telling the IOMMU or some other allocator that you are allocating N bytes, but freeing N-M bytes. IOW, a leak.

Now that that's been clarified, please fix up the patch and resubmit... with this issue fixed, it looks apply-able.

        Jeff




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