Re: [PATCH 1/3] net: dsa: lantiq_gswip: fix use-after-free on failed probe

[Andrew Lunn <andrew@lunn.ch>]

On Wed, Jan 16, 2019 at 11:23:33AM +0100, Johan Hovold wrote:
> Make sure to disable and deregister the switch on late probe errors to
> avoid use-after-free when the device-resource-managed switch is freed.
> 
> Fixes: 14fceff4771e ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
> Cc: stable <stable@vger.kernel.org>	# 4.20
> Cc: Hauke Mehrtens <hauke@hauke-m.de>
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/net/dsa/lantiq_gswip.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/lantiq_gswip.c b/drivers/net/dsa/lantiq_gswip.c
> index 693a67f45bef..b06c41c98de9 100644
> --- a/drivers/net/dsa/lantiq_gswip.c
> +++ b/drivers/net/dsa/lantiq_gswip.c
> @@ -1099,7 +1099,7 @@ static int gswip_probe(struct platform_device *pdev)
>  		dev_err(dev, "wrong CPU port defined, HW only supports port: %i",
>  			priv->hw_info->cpu_port);
>  		err = -EINVAL;
> -		goto mdio_bus;
> +		goto disable_switch;
>  	}
>  
>  	platform_set_drvdata(pdev, priv);
> @@ -1109,6 +1109,9 @@ static int gswip_probe(struct platform_device *pdev)
>  		 (version & GSWIP_VERSION_MOD_MASK) >> GSWIP_VERSION_MOD_SHIFT);
>  	return 0;
>  
> +disable_switch:
> +	gswip_mdio_mask(priv, GSWIP_MDIO_GLOB_ENABLE, 0, GSWIP_MDIO_GLOB);
> +	dsa_unregister_switch(priv->ds);

This is correct. But it would be nice if somebody in the future could
move the disabling of the switch to the inverse of the gswip_setup()
function to make the code symmetrical.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew