Re: [PATCH] net: lpc_eth: Fix a possible memory leak in lpc_mii_probe()

[Vladimir Zapolskiy <vz@mleia.com>]

Hello Ma Ke,

On 3/30/26 11:16, Ma Ke wrote:
> lpc_mii_probe() calls of_phy_find_device() to obtain a phy_device
> pointer. of_phy_find_device() increments the refcount of the device.
> The current implementation does not decrement the refcount after using
> the pointer, which leads to a memory leak.

this is correct, there is an actual detected bug.

> 
> Add phy_device_free() to balance the refcount.

But this does not sound right, you shoud use of_node_put(pldat->phy_node).

> 
> Found by code review.
> 
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> Cc: stable@vger.kernel.org
> Fixes: 3503bf024b3e ("net: lpc_eth: parse phy nodes from device tree")
> ---
>   drivers/net/ethernet/nxp/lpc_eth.c | 11 ++++++-----
>   1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/nxp/lpc_eth.c b/drivers/net/ethernet/nxp/lpc_eth.c
> index 8b9a3e3bba30..8ce7c9bb6dd6 100644
> --- a/drivers/net/ethernet/nxp/lpc_eth.c
> +++ b/drivers/net/ethernet/nxp/lpc_eth.c
> @@ -751,7 +751,7 @@ static void lpc_handle_link_change(struct net_device *ndev)
>   static int lpc_mii_probe(struct net_device *ndev)
>   {
>   	struct netdata_local *pldat = netdev_priv(ndev);
> -	struct phy_device *phydev;
> +	struct phy_device *phydev, *phydev_tmp;
>   
>   	/* Attach to the PHY */
>   	if (lpc_phy_interface_mode(&pldat->pdev->dev) == PHY_INTERFACE_MODE_MII)
> @@ -760,17 +760,18 @@ static int lpc_mii_probe(struct net_device *ndev)
>   		netdev_info(ndev, "using RMII interface\n");
>   
>   	if (pldat->phy_node)
> -		phydev =  of_phy_find_device(pldat->phy_node);
> +		phydev_tmp =  of_phy_find_device(pldat->phy_node);
>   	else
> -		phydev = phy_find_first(pldat->mii_bus);
> -	if (!phydev) {
> +		phydev_tmp = phy_find_first(pldat->mii_bus);
> +	if (!phydev_tmp) {

I didn't get it, why the new phydev_tmp is needed above, please
restore the original code above.

>   		netdev_err(ndev, "no PHY found\n");
>   		return -ENODEV;
>   	}
>   
> -	phydev = phy_connect(ndev, phydev_name(phydev),
> +	phydev = phy_connect(ndev, phydev_name(phydev_tmp),
>   			     &lpc_handle_link_change,
>   			     lpc_phy_interface_mode(&pldat->pdev->dev));
> +	phy_device_free(phydev_tmp);

This is plainly wrong and has to be dropped or changed to

	if (pldat->phy_node)
		of_node_put(pldat->phy_node);

>   	if (IS_ERR(phydev)) {
>   		netdev_err(ndev, "Could not attach to PHY\n");
>   		return PTR_ERR(phydev);

Is it AI generated fix or what?.. The change looks bad, it introduces
more severe issues than it fixes.

If you think you cannot create a proper change, let me know.

-- 
Best wishes,
Vladimir