netdev - [PATCH V2 net] net: fec: Coverity issue: Dereference null return value

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Message-Id: <20221219022755.1047573-1-wei.fang@nxp.com>
Date:   Mon, 19 Dec 2022 10:27:55 +0800
From:   wei.fang@....com
To:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, xiaoning.wang@....com, shenwei.wang@....com,
        alexander.duyck@...il.com, linux-imx@....com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH V2 net] net: fec: Coverity issue: Dereference null return value

From: Wei Fang <wei.fang@....com>

The build_skb might return a null pointer but there is no check on the
return value in the fec_enet_rx_queue(). So a null pointer dereference
might occur. To avoid this, we check the return value of build_skb. If
the return value is a null pointer, the driver will recycle the page and
update the statistic of ndev. Then jump to rx_processing_done to clear
the status flags of the BD so that the hardware can recycle the BD.

Signed-off-by: Wei Fang <wei.fang@....com>
Reviewed-by: Shenwei Wang <Shenwei.wang@....com>
---
V2 changes:
1. Remove rx_packets and rx_bytes counters.
2. Use netdev_err_once instead of netdev_err.
---
 drivers/net/ethernet/freescale/fec_main.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 5528b0af82ae..644f3c963730 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1674,6 +1674,14 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
 		 * bridging applications.
 		 */
 		skb = build_skb(page_address(page), PAGE_SIZE);
+		if (unlikely(!skb)) {
+			page_pool_recycle_direct(rxq->page_pool, page);
+			ndev->stats.rx_dropped++;
+
+			netdev_err_once(ndev, "build_skb failed!\n");
+			goto rx_processing_done;
+		}
+
 		skb_reserve(skb, data_start);
 		skb_put(skb, pkt_len - sub_len);
 		skb_mark_for_recycle(skb);
-- 
2.25.1