Subject: Re: [PATCH 1/1] net: dsa: Fix of kernel panic in case of missing PHY.

From: Florian Fainelli <[email-masked]>
Date: Tue, 09 Dec 2014 19:23:38 -0800

On 09/12/14 09:31, Andrey Volkov wrote:
> Fix of kernel panic in case of missing PHY.
> 
> Signed-off-by: Andrey Volkov <[email-masked]>

Brian has actually been able to reproduce such a crash in this code-path
today:

if (!p->phy) {
                p->phy = ds->slave_mii_bus->phy_map[p->port];
                phy_connect_direct(slave_dev, p->phy,
				   dsa_slave_adjust_link,
                                   p->phy_interface);
}

we basically assume here that we have a valid phy pointer out of
ds->slave_mii_bus->phy_map[p->port] which is not true in all cases,
especially not if the device is not there.

I will come up with a fix for that, as for propagating the error code
down to the caller, this can be a separate patch.

Thanks!

> ---
>  net/dsa/slave.c |   19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 528380a..6f89caa 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -512,7 +512,7 @@ static int dsa_slave_fixed_link_update(struct net_device *dev,
>  }
>  
>  /* slave device setup *******************************************************/
> -static void dsa_slave_phy_setup(struct dsa_slave_priv *p,
> +static int dsa_slave_phy_setup(struct dsa_slave_priv *p,
>  				struct net_device *slave_dev)
>  {
>  	struct dsa_switch *ds = p->parent;
> @@ -533,7 +533,7 @@ static void dsa_slave_phy_setup(struct dsa_slave_priv *p,
>  		ret = of_phy_register_fixed_link(port_dn);
>  		if (ret) {
>  			netdev_err(slave_dev, "failed to register fixed PHY\n");
> -			return;
> +			return ret;
>  		}
>  		phy_is_fixed = true;
>  		phy_dn = port_dn;
> @@ -555,12 +555,17 @@ static void dsa_slave_phy_setup(struct dsa_slave_priv *p,
>  	 */
>  	if (!p->phy) {
>  		p->phy = ds->slave_mii_bus->phy_map[p->port];
> -		phy_connect_direct(slave_dev, p->phy, dsa_slave_adjust_link,
> +		if(p->phy)
> +			phy_connect_direct(slave_dev, p->phy, dsa_slave_adjust_link,
>  				   p->phy_interface);
> +		else
> +			return -ENODEV;
> +
>  	} else {
>  		netdev_info(slave_dev, "attached PHY at address %d [%s]\n",
>  			    p->phy->addr, p->phy->drv->name);
>  	}
> +	return 0;
>  }
>  
>  int dsa_slave_suspend(struct net_device *slave_dev)
> @@ -653,7 +658,13 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
>  	p->old_link = -1;
>  	p->old_duplex = -1;
>  
> -	dsa_slave_phy_setup(p, slave_dev);
> +	ret = dsa_slave_phy_setup(p, slave_dev);
> +	if (ret) {
> +		netdev_err(master, "error %d registering interface %s\n",
> +			   ret, slave_dev->name);
> +		free_netdev(slave_dev);
> +		return NULL;
> +	}
>  
>  	ret = register_netdev(slave_dev);
>  	if (ret) {
>