linux-kernel - [PATCH net] net: lantiq_xrx200: fix use after free bug

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Message-Id: <20220305112039.3989-1-olek2@wp.pl>
Date:   Sat,  5 Mar 2022 12:20:39 +0100
From:   Aleksander Jan Bajkowski <olek2@...pl>
To:     hauke@...ke-m.de, davem@...emloft.net, kuba@...nel.org,
        olek2@...pl, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net] net: lantiq_xrx200: fix use after free bug

The skb->len field is read after the packet is sent to the network
stack. In the meantime, skb can be freed. This patch fixes this bug.

Fixes: c3e6b2c35b34 ("net: lantiq_xrx200: add ingress SG DMA support")
Reported-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Aleksander Jan Bajkowski <olek2@...pl>
---
 drivers/net/ethernet/lantiq_xrx200.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
index 41d11137cde0..5712c3e94be8 100644
--- a/drivers/net/ethernet/lantiq_xrx200.c
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -260,9 +260,9 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
 
 	if (ctl & LTQ_DMA_EOP) {
 		ch->skb_head->protocol = eth_type_trans(ch->skb_head, net_dev);
-		netif_receive_skb(ch->skb_head);
 		net_dev->stats.rx_packets++;
 		net_dev->stats.rx_bytes += ch->skb_head->len;
+		netif_receive_skb(ch->skb_head);
 		ch->skb_head = NULL;
 		ch->skb_tail = NULL;
 		ret = XRX200_DMA_PACKET_COMPLETE;
-- 
2.30.2