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

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Message-ID: <20250801101154.GK8494@horms.kernel.org>
Date: Fri, 1 Aug 2025 11:11:54 +0100
From: Simon Horman <horms@...nel.org>
To: Jijie Shao <shaojijie@...wei.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, andrew+netdev@...n.ch, 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
Subject: Re: [PATCH net 2/3] net: hibmcge: fix the division by zero issue

On Thu, Jul 31, 2025 at 09:47:48PM +0800, Jijie Shao wrote:
> 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>

Thanks,

Thinking aloud:

I see that hbg_get_queue_used_num() can be called for both RX and TX
rings via the debugfs code hbg_dbg_ring(). And that hbg_net_stop()
clears the RX and TX ring configuration using hbg_txrx_uninit().

So I agree that when the port is down ring-len will be 0.

Reviewed-by: Simon Horman <horms@...nel.org>