netdev - Re: [Intel-wired-lan] [PATCH] i40e: Fix potential invalid access when MAC list is empty

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Message-ID: <6dc3bd8e-66db-4237-86bc-717f7b5c7b2a@molgen.mpg.de>
Date: Wed, 27 Aug 2025 17:18:34 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Zhen Ni <zhen.ni@...ystack.cn>
Cc: anthony.l.nguyen@...el.com, przemyslaw.kitszel@...el.com,
 andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, intel-wired-lan@...ts.osuosl.org,
 netdev@...r.kernel.org
Subject: Re: [Intel-wired-lan] [PATCH] i40e: Fix potential invalid access when
 MAC list is empty

Dear Zhen,


Thank you for your patch.

Am 27.08.25 um 05:23 schrieb Zhen Ni:
> list_first_entry() never returns NULL — if the list is empty, it still
> returns a pointer to an invalid object, leading to potential invalid
> memory access when dereferenced.
> 
> Fix this by checking list_empty() before calling list_first_entry(),
> and only copying the MAC address when the list is not empty.
> 
> Fixes: e3219ce6a775 ("i40e: Add support for client interface for IWARP driver")
> Signed-off-by: Zhen Ni <zhen.ni@...ystack.cn>
> ---
>   drivers/net/ethernet/intel/i40e/i40e_client.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_client.c b/drivers/net/ethernet/intel/i40e/i40e_client.c
> index 5f1a405cbbf8..0a72157aee0e 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_client.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_client.c
> @@ -359,12 +359,13 @@ static void i40e_client_add_instance(struct i40e_pf *pf)
>   	if (i40e_client_get_params(vsi, &cdev->lan_info.params))
>   		goto free_cdev;
>   
> -	mac = list_first_entry(&cdev->lan_info.netdev->dev_addrs.list,
> -			       struct netdev_hw_addr, list);
> -	if (mac)
> +	if (!list_empty(&cdev->lan_info.netdev->dev_addrs.list)) {
> +		mac = list_first_entry(&cdev->lan_info.netdev->dev_addrs.list,
> +				       struct netdev_hw_addr, list);
>   		ether_addr_copy(cdev->lan_info.lanmac, mac->addr);
> -	else
> +	} else {
>   		dev_err(&pf->pdev->dev, "MAC address list is empty!\n");
> +	}
>   
>   	pf->cinst = cdev;
>   

Reviewed-by: Paul Menzel <pmenzel@...gen.mpg.de>


Kind regards,

Paul