netdev - Re: [PATCH v2 5/6] net: dsa: add missing calls in dsa_switch

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Message-ID: <20151029140058.GS2307@lunn.ch>
Date:	Thu, 29 Oct 2015 15:00:58 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Neil Armstrong <narmstrong@...libre.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	vivien.didelot@...oirfairelinux.com,
	Fabian Frederick <fabf@...net.be>,
	Pavel Nakonechny <pavel.nakonechny@...tlab.ru>,
	Joe Perches <joe@...ches.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Frode Isaksen <fisaksen@...libre.com>
Subject: Re: [PATCH v2 5/6] net: dsa: add missing calls in dsa_switch_destroy

On Thu, Oct 29, 2015 at 02:23:25PM +0100, Neil Armstrong wrote:
> Add missing netif_carrier_off and phy_disconnect calls to the
> dsa_switch_destroy function to make sure the netdev and phy
> ressources are clean before complete removal.
> 
> Signed-off-by: Frode Isaksen <fisaksen@...libre.com>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  net/dsa/dsa.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index 597a462..11452e4 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -454,7 +454,9 @@ static void dsa_switch_destroy(struct dsa_switch *ds)
>  		if (!ds->ports[port])
>  			continue;
> 
> +		netif_carrier_off(ds->ports[port]);
>  		unregister_netdev(ds->ports[port]);
> +		phy_disconnect(p->phy);
>  		free_netdev(ds->ports[port]);
>  	}

Once you make it actually compile....

I'm not sure this is safe. The loop above this one has just destroyed
some phys, and now you are potentially disconnecting a phy you just
destroyed, causing it to be accessed?

I would suggest you first fix the ordering in dsa_switch_destroy()
and then add the missing netif_carrier_off() and phy_disconnect().

Thanks
	Andrew
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