netdev - [PATCH net 2/3] net: ethernet: ti: am65-cpsw: Fix NULL dereference on XDP

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Message-Id: <20240829-am65-cpsw-xdp-v1-2-ff3c81054a5e@kernel.org>
Date: Thu, 29 Aug 2024 15:03:20 +0300
From: Roger Quadros <rogerq@...nel.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 Julien Panis <jpanis@...libre.com>, Jacob Keller <jacob.e.keller@...el.com>
Cc: Siddharth Vadapalli <s-vadapalli@...com>, 
 Md Danish Anwar <danishanwar@...com>, Vignesh Raghavendra <vigneshr@...com>, 
 Govindarajan Sriramakrishnan <srk@...com>, netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
 Roger Quadros <rogerq@...nel.org>
Subject: [PATCH net 2/3] net: ethernet: ti: am65-cpsw: Fix NULL dereference
 on XDP_TX

If number of TX queues are set to 1 we get a NULL pointer
dereference during XDP_TX.

~# ethtool -L eth0 tx 1
~# ./xdp-trafficgen udp -A <ipv6-src> -a <ipv6-dst> eth0 -t 2
Transmitting on eth0 (ifindex 2)
[  241.135257] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030

Fix this by using actual TX queues instead of max TX queues
when picking the TX channel in am65_cpsw_ndo_xdp_xmit().

Fixes: 8acacc40f733 ("net: ethernet: ti: am65-cpsw: Add minimal XDP support")
Signed-off-by: Roger Quadros <rogerq@...nel.org>
---
 drivers/net/ethernet/ti/am65-cpsw-nuss.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
index 9fd2ba26716c..03577a008df2 100644
--- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
+++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
@@ -1924,12 +1924,13 @@ static int am65_cpsw_ndo_bpf(struct net_device *ndev, struct netdev_bpf *bpf)
 static int am65_cpsw_ndo_xdp_xmit(struct net_device *ndev, int n,
 				  struct xdp_frame **frames, u32 flags)
 {
+	struct am65_cpsw_common *common = am65_ndev_to_common(ndev);
 	struct am65_cpsw_tx_chn *tx_chn;
 	struct netdev_queue *netif_txq;
 	int cpu = smp_processor_id();
 	int i, nxmit = 0;

-	tx_chn = &am65_ndev_to_common(ndev)->tx_chns[cpu % AM65_CPSW_MAX_TX_QUEUES];
+	tx_chn = &common->tx_chns[cpu % common->tx_ch_num];
 	netif_txq = netdev_get_tx_queue(ndev, tx_chn->id);

 	__netif_tx_lock(netif_txq, cpu);

-- 
2.34.1