From: Sean Anderson seanga2@gmail.com
[ Upstream commit 878e2405710aacfeeb19364c300f38b7a9abfe8f ]
There is a separate receive path for small packets (under 256 bytes). Instead of allocating a new dma-capable skb to be used for the next packet, this path allocates a skb and copies the data into it (reusing the existing sbk for the next packet). There are two bytes of junk data at the beginning of every packet. I believe these are inserted in order to allow aligned DMA and IP headers. We skip over them using skb_reserve. Before copying over the data, we must use a barrier to ensure we see the whole packet. The current code only synchronizes len bytes, starting from the beginning of the packet, including the junk bytes. However, this leaves off the final two bytes in the packet. Synchronize the whole packet.
To reproduce this problem, ping a HME with a payload size between 17 and 214
$ ping -s 17 <hme_address>
which will complain rather loudly about the data mismatch. Small packets (below 60 bytes on the wire) do not have this issue. I suspect this is related to the padding added to increase the minimum packet size.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Sean Anderson seanga2@gmail.com Reviewed-by: Andrew Lunn andrew@lunn.ch Link: https://lore.kernel.org/r/20220920235018.1675956-1-seanga2@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/sun/sunhme.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/sun/sunhme.c b/drivers/net/ethernet/sun/sunhme.c index 882908e74cc9..a4090163d870 100644 --- a/drivers/net/ethernet/sun/sunhme.c +++ b/drivers/net/ethernet/sun/sunhme.c @@ -2064,9 +2064,9 @@ static void happy_meal_rx(struct happy_meal *hp, struct net_device *dev)
skb_reserve(copy_skb, 2); skb_put(copy_skb, len); - dma_sync_single_for_cpu(hp->dma_dev, dma_addr, len, DMA_FROM_DEVICE); + dma_sync_single_for_cpu(hp->dma_dev, dma_addr, len + 2, DMA_FROM_DEVICE); skb_copy_from_linear_data(skb, copy_skb->data, len); - dma_sync_single_for_device(hp->dma_dev, dma_addr, len, DMA_FROM_DEVICE); + dma_sync_single_for_device(hp->dma_dev, dma_addr, len + 2, DMA_FROM_DEVICE); /* Reuse original ring buffer. */ hme_write_rxd(hp, this, (RXFLAG_OWN|((RX_BUF_ALLOC_SIZE-RX_OFFSET)<<16)),