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

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Date:   Wed, 16 Jan 2019 22:43:58 +0100
From:   Hauke Mehrtens <hauke@...ke-m.de>
To:     Andrew Lunn <andrew@...n.ch>, Johan Hovold <johan@...nel.org>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH 1/3] net: dsa: lantiq_gswip: fix use-after-free on failed
 probe

On 1/16/19 4:00 PM, Andrew Lunn wrote:
> 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@...r.kernel.org>	# 4.20
>> Cc: Hauke Mehrtens <hauke@...ke-m.de>
>> Signed-off-by: Johan Hovold <johan@...nel.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.

Should we add an uninit callback?

Hauke