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Date: Sun, 20 Sep 2026 10:25:12 +0100
From: Simon Horman <horms@kernel.org>
To: Wentao Liang <vulab@iscas.ac.cn>
Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com,
	kuba@kernel.org, linux-kernel@vger.kernel.org, mchan@broadcom.com,
	netdev@vger.kernel.org, pabeni@redhat.com,
	pavan.chebbi@broadcom.com, stable@vger.kernel.org
Subject: Re: [PATCH] tg3: Fix peer device double put in tg3_find_peer()
Message-ID: <20260920092512.GA13925@horms.kernel.org>
References: <20260917105104.2147646-1-vulab@iscas.ac.cn>
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In-Reply-To: <20260917105104.2147646-1-vulab@iscas.ac.cn>

On Thu, Sep 17, 2026 at 10:51:04AM +0000, Wentao Liang wrote:
> pci_get_slot() returns a device with its reference count incremented.
> When the loop ends on tp->pdev (which happens when the adapter sits at
> PCI function 7 and no other function is present) that reference has
> already been dropped inside the loop, but the trailing pci_dev_put()
> drops it a second time, underflowing the refcount of tp->pdev.
> 
> Treat a loop end on tp->pdev as single-port mode, just like the
> existing !peer case.
> 
> Fixes: 16fe9d74f14e ("[TG3]: Fix 5704 single-port mode")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>

Hi,

I agree with your analysis of the logic.
But I wonder if it can occur in practice:
can such a device actually be presented to the Kernel?