netdev - [PATCH net 2/3] net: hibmcge: fix the division by zero issue

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Message-ID: <20250731134749.4090041-3-shaojijie@huawei.com>
Date: Thu, 31 Jul 2025 21:47:48 +0800
From: Jijie Shao <shaojijie@...wei.com>
To: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <andrew+netdev@...n.ch>, <horms@...nel.org>
CC: <shenjian15@...wei.com>, <liuyonglong@...wei.com>,
	<chenhao418@...wei.com>, <jonathan.cameron@...wei.com>,
	<shameerali.kolothum.thodi@...wei.com>, <salil.mehta@...wei.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<shaojijie@...wei.com>
Subject: [PATCH net 2/3] net: hibmcge: fix the division by zero issue

When the network port is down, the queue is released, and ring->len is 0.
In debugfs, hbg_get_queue_used_num() will be called,
which may lead to a division by zero issue.

This patch adds a check, if ring->len is 0,
hbg_get_queue_used_num() directly returns 0.

Fixes: 40735e7543f9 ("net: hibmcge: Implement .ndo_start_xmit function")
Signed-off-by: Jijie Shao <shaojijie@...wei.com>
---
 drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h b/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h
index 2883a5899ae2..2aecc73f3d49 100644
--- a/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h
+++ b/drivers/net/ethernet/hisilicon/hibmcge/hbg_txrx.h
@@ -29,6 +29,9 @@ static inline bool hbg_fifo_is_full(struct hbg_priv *priv, enum hbg_dir dir)
 
 static inline u32 hbg_get_queue_used_num(struct hbg_ring *ring)
 {
+	if (!ring->len)
+		return 0;
+
 	return (ring->ntu + ring->len - ring->ntc) % ring->len;
 }
 
-- 
2.33.0