netdev - [PATCH net] net: ethernet: ti: am65-cpsw: Fix NAPI registration sequence

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Message-ID: <20250311061214.4111634-1-s-vadapalli@ti.com>
Date: Tue, 11 Mar 2025 11:42:14 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: <andrew+netdev@...n.ch>, <davem@...emloft.net>, <edumazet@...gle.com>,
        <kuba@...nel.org>, <pabeni@...hat.com>, <rogerq@...nel.org>,
        <horms@...nel.org>, <alexander.sverdlin@...mens.com>,
        <dan.carpenter@...aro.org>, <jpanis@...libre.com>
CC: <vigneshr@...com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <srk@...com>, <s-vadapalli@...com>
Subject: [PATCH net] net: ethernet: ti: am65-cpsw: Fix NAPI registration sequence

From: Vignesh Raghavendra <vigneshr@...com>

Registering the interrupts for TX or RX DMA Channels prior to registering
their respective NAPI callbacks can result in a NULL pointer dereference.
This is seen in practice as a random occurrence since it depends on the
randomness associated with the generation of traffic by Linux and the
reception of traffic from the wire.

Fixes: 681eb2beb3ef ("net: ethernet: ti: am65-cpsw: ensure proper channel cleanup in error path")
Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
Co-developed-by: Siddharth Vadapalli <s-vadapalli@...com>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
---

Hello,

This patch is based on commit
4d872d51bc9d Merge tag 'x86-urgent-2025-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
of Mainline Linux.

Regards,
Siddharth.

 drivers/net/ethernet/ti/am65-cpsw-nuss.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
index 2806238629f8..d5291281c781 100644
--- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
+++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
@@ -2314,6 +2314,9 @@ static int am65_cpsw_nuss_ndev_add_tx_napi(struct am65_cpsw_common *common)
 		hrtimer_init(&tx_chn->tx_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
 		tx_chn->tx_hrtimer.function = &am65_cpsw_nuss_tx_timer_callback;
 
+		netif_napi_add_tx(common->dma_ndev, &tx_chn->napi_tx,
+				  am65_cpsw_nuss_tx_poll);
+
 		ret = devm_request_irq(dev, tx_chn->irq,
 				       am65_cpsw_nuss_tx_irq,
 				       IRQF_TRIGGER_HIGH,
@@ -2323,9 +2326,6 @@ static int am65_cpsw_nuss_ndev_add_tx_napi(struct am65_cpsw_common *common)
 				tx_chn->id, tx_chn->irq, ret);
 			goto err;
 		}
-
-		netif_napi_add_tx(common->dma_ndev, &tx_chn->napi_tx,
-				  am65_cpsw_nuss_tx_poll);
 	}
 
 	return 0;
@@ -2569,6 +2569,9 @@ static int am65_cpsw_nuss_init_rx_chns(struct am65_cpsw_common *common)
 			     HRTIMER_MODE_REL_PINNED);
 		flow->rx_hrtimer.function = &am65_cpsw_nuss_rx_timer_callback;
 
+		netif_napi_add(common->dma_ndev, &flow->napi_rx,
+			       am65_cpsw_nuss_rx_poll);
+
 		ret = devm_request_irq(dev, flow->irq,
 				       am65_cpsw_nuss_rx_irq,
 				       IRQF_TRIGGER_HIGH,
@@ -2579,9 +2582,6 @@ static int am65_cpsw_nuss_init_rx_chns(struct am65_cpsw_common *common)
 			flow->irq = -EINVAL;
 			goto err_flow;
 		}
-
-		netif_napi_add(common->dma_ndev, &flow->napi_rx,
-			       am65_cpsw_nuss_rx_poll);
 	}
 
 	/* setup classifier to route priorities to flows */
-- 
2.34.1