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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Aleksander Jan Bajkowski <olek2@wp.pl>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 066/178] lantiq: net: fix duplicated skb in rx descriptor ring
Date:   Mon, 21 Jun 2021 18:14:40 +0200
Message-Id: <20210621154924.755623998@linuxfoundation.org>
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From: Aleksander Jan Bajkowski <olek2@wp.pl>

[ 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>
---
 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 3da494df72f3..072075bc60ee 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