lantiq: net: fix duplicated skb in rx descriptor ring

[ Upstream commit 7ea6cd16f1599c1eac6018751eadbc5fc736b99a ]

The previous commit didn't fix the bug properly. By mistake, it replaces
the pointer of the next skb in the descriptor ring instead of the current
one. As a result, the two descriptors are assigned the same SKB. The error
is seen during the iperf test when skb_put tries to insert a second packet
and exceeds the available buffer.

Fixes: c7718ee96dbc ("net: lantiq: fix memory corruption in RX ring ")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
index 8d073b895fc0d84f7ecd63001d6d5e88654ca1bd..6e504854571cfc656d7e5ebadda10c3aebd26ca0 100644 (file)
--- a/drivers/net/ethernet/lantiq_xrx200.c
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -154,6 +154,7 @@ static int xrx200_close(struct net_device *net_dev)
 
 static int xrx200_alloc_skb(struct xrx200_chan *ch)
 {
+       struct sk_buff *skb = ch->skb[ch->dma.desc];
        dma_addr_t mapping;
        int ret = 0;
 
@@ -168,6 +169,7 @@ static int xrx200_alloc_skb(struct xrx200_chan *ch)
                                 XRX200_DMA_DATA_LEN, DMA_FROM_DEVICE);
        if (unlikely(dma_mapping_error(ch->priv->dev, mapping))) {
                dev_kfree_skb_any(ch->skb[ch->dma.desc]);
+               ch->skb[ch->dma.desc] = skb;
                ret = -ENOMEM;
                goto skip;
        }
@@ -198,7 +200,6 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
        ch->dma.desc %= LTQ_DESC_NUM;
 
        if (ret) {
-               ch->skb[ch->dma.desc] = skb;
                net_dev->stats.rx_dropped++;
                netdev_err(net_dev, "failed to allocate new rx buffer\n");
                return ret;