linux-kernel - Re: [PATCH net v1] lan78xx: Fix crash with multiple device attach

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Date: Mon, 06 May 2024 11:38:29 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Rengarajan S <rengarajan.s@...rochip.com>, woojung.huh@...rochip.com, 
	UNGLinuxDriver@...rochip.com, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, netdev@...r.kernel.org, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v1] lan78xx: Fix crash with multiple device attach

On Thu, 2024-05-02 at 10:27 +0530, Rengarajan S wrote:
> After the first device(MAC + PHY) is attached, the corresponding
> fixup gets registered and before it is unregistered next device
> is attached causing the dev pointer of second device to be NULL.
> Fixed the issue with multiple PHY attach by unregistering PHY
> at the end of probe. Removed the unregistration during phy_init
> since the handling has been taken care in probe.

The above description is unclear to me. Could you please list the exact
sequence of events/calls that lead to the problem?

> Fixes: 89b36fb5e532 ("lan78xx: Lan7801 Support for Fixed PHY")
> Signed-off-by: Rengarajan S <rengarajan.s@...rochip.com>
> ---
> 
>  drivers/net/usb/lan78xx.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
> index 5add4145d..3ec79620f 100644
> --- a/drivers/net/usb/lan78xx.c
> +++ b/drivers/net/usb/lan78xx.c
> @@ -2383,14 +2383,8 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
>  		netdev_err(dev->net, "can't attach PHY to %s\n",
>  			   dev->mdiobus->id);
>  		if (dev->chipid == ID_REV_CHIP_ID_7801_) {
> -			if (phy_is_pseudo_fixed_link(phydev)) {
> +			if (phy_is_pseudo_fixed_link(phydev))
>  				fixed_phy_unregister(phydev);
> -			} else {
> -				phy_unregister_fixup_for_uid(PHY_KSZ9031RNX,
> -							     0xfffffff0);
> -				phy_unregister_fixup_for_uid(PHY_LAN8835,
> -							     0xfffffff0);
> -			}
>  		}
>  		return -EIO;
>  	}
> @@ -4458,6 +4452,14 @@ static int lan78xx_probe(struct usb_interface *intf,
>  	pm_runtime_set_autosuspend_delay(&udev->dev,
>  					 DEFAULT_AUTOSUSPEND_DELAY);
>  
> +	/* Unregistering Fixup to avoid crash with multiple device
> +	 * attach.
> +	 */
> +	phy_unregister_fixup_for_uid(PHY_KSZ9031RNX,
> +				     0xfffffff0);
> +	phy_unregister_fixup_for_uid(PHY_LAN8835,
> +				     0xfffffff0);
> +

Minor nit: the above 2 statments can now fit a single line each.

Thanks,

Paolo