[PATCH net v2] lantiq: net: fix duplicated skb in rx descriptor ring

From: Aleksander Jan Bajkowski <olek2@wp.pl>
To: hauke@hauke-m.de, davem@davemloft.net, kuba@kernel.org,
	olek2@wp.pl, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH net v2] lantiq: net: fix duplicated skb in rx descriptor ring
Date: Tue, 15 Jun 2021 22:42:57 +0200	[thread overview]
Message-ID: <20210615204257.217653-1-olek2@wp.pl> (raw)

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>
---
 drivers/net/ethernet/lantiq_xrx200.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
index 36dc3e5f6218..f92046dff227 100644
--- 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;
-- 
2.30.2

