linux-kernel - [PATCH net 4/4] net: ti: icssg-prueth: Fix kernel panic during concurrent Tx queue access

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Message-ID: <20250428120459.244525-5-m-malladi@ti.com>
Date: Mon, 28 Apr 2025 17:34:59 +0530
From: Meghana Malladi <m-malladi@...com>
To: <dan.carpenter@...aro.org>, <m-malladi@...com>, <john.fastabend@...il.com>,
        <hawk@...nel.org>, <daniel@...earbox.net>, <ast@...nel.org>,
        <pabeni@...hat.com>, <kuba@...nel.org>, <edumazet@...gle.com>,
        <davem@...emloft.net>, <andrew+netdev@...n.ch>
CC: <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <srk@...com>, Vignesh Raghavendra <vigneshr@...com>,
        Roger Quadros
	<rogerq@...nel.org>, <danishanwar@...com>
Subject: [PATCH net 4/4] net: ti: icssg-prueth: Fix kernel panic during concurrent Tx queue access

Add __netif_tx_lock() to ensure that only one packet is being
transmitted at a time to avoid race conditions in the netif_txq
struct and prevent packet data corruption. Failing to do so causes
kernel panic with the following error:

[ 2184.746764] ------------[ cut here ]------------
[ 2184.751412] kernel BUG at lib/dynamic_queue_limits.c:99!
[ 2184.756728] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP

logs: https://gist.github.com/MeghanaMalladiTI/9c7aa5fc3b7fb03f87c74aad487956e9

The lock is acquired before calling emac_xmit_xdp_frame() and released after the
call returns. This ensures that the TX queue is protected from concurrent access
during the transmission of XDP frames.

Fixes: 62aa3246f462 ("net: ti: icssg-prueth: Add XDP support")
Signed-off-by: Meghana Malladi <m-malladi@...com>
---
 drivers/net/ethernet/ti/icssg/icssg_common.c | 7 ++++++-
 drivers/net/ethernet/ti/icssg/icssg_prueth.c | 7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
index a120ff6fec8f..e509b6ff81e7 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_common.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
@@ -660,6 +660,8 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp,
 			struct page *page, u32 *len)
 {
 	struct net_device *ndev = emac->ndev;
+	struct netdev_queue *netif_txq;
+	int cpu = smp_processor_id();
 	struct bpf_prog *xdp_prog;
 	struct xdp_frame *xdpf;
 	u32 pkt_len = *len;
@@ -679,8 +681,11 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp,
 			goto drop;
 		}
 
-		q_idx = smp_processor_id() % emac->tx_ch_num;
+		q_idx = cpu % emac->tx_ch_num;
+		netif_txq = netdev_get_tx_queue(ndev, q_idx);
+		__netif_tx_lock(netif_txq, cpu);
 		result = emac_xmit_xdp_frame(emac, xdpf, page, q_idx);
+		__netif_tx_unlock(netif_txq);
 		if (result == ICSSG_XDP_CONSUMED) {
 			ndev->stats.tx_dropped++;
 			goto drop;
diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.c b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
index ee35fecf61e7..b31060e7f698 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_prueth.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
@@ -1075,20 +1075,25 @@ static int emac_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frame
 {
 	struct prueth_emac *emac = netdev_priv(dev);
 	struct net_device *ndev = emac->ndev;
+	struct netdev_queue *netif_txq;
+	int cpu = smp_processor_id();
 	struct xdp_frame *xdpf;
 	unsigned int q_idx;
 	int nxmit = 0;
 	u32 err;
 	int i;
 
-	q_idx = smp_processor_id() % emac->tx_ch_num;
+	q_idx = cpu % emac->tx_ch_num;
+	netif_txq = netdev_get_tx_queue(ndev, q_idx);
 
 	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
 		return -EINVAL;
 
 	for (i = 0; i < n; i++) {
 		xdpf = frames[i];
+		__netif_tx_lock(netif_txq, cpu);
 		err = emac_xmit_xdp_frame(emac, xdpf, NULL, q_idx);
+		__netif_tx_unlock(netif_txq);
 		if (err != ICSSG_XDP_TX) {
 			ndev->stats.tx_dropped++;
 			break;
-- 
2.43.0