netdev - Re: [PATCH net] net: dsa: Discard frames from unused ports

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Message-ID: <ac81103a-97f4-c7ae-3f12-c78e617f4edc@gmail.com>
Date:   Wed, 4 Apr 2018 17:49:10 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Subject: Re: [PATCH net] net: dsa: Discard frames from unused ports

On 04/04/2018 04:56 PM, Andrew Lunn wrote:
> The Marvell switches under some conditions will pass a frame to the
> host with the port being the CPU port. Such frames are invalid, and
> should be dropped. Not dropping them can result in a crash when
> incrementing the receive statistics for an invalid port.
> 
> Reported-by: Chris Healy <cphealy@...il.com>
> Fixes: 5f6b4e14cada ("net: dsa: User per-cpu 64-bit statistics")

Are you sure this is the commit that introduced the problem?

> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---
>  net/dsa/dsa_priv.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
> index 70de7895e5b8..6c1bf3d9f652 100644
> --- a/net/dsa/dsa_priv.h
> +++ b/net/dsa/dsa_priv.h
> @@ -126,6 +126,7 @@ static inline struct net_device *dsa_master_find_slave(struct net_device *dev,
>  	struct dsa_port *cpu_dp = dev->dsa_ptr;
>  	struct dsa_switch_tree *dst = cpu_dp->dst;
>  	struct dsa_switch *ds;
> +	struct dsa_port *slave_port;
>  
>  	if (device < 0 || device >= DSA_MAX_SWITCHES)
>  		return NULL;
> @@ -137,7 +138,12 @@ static inline struct net_device *dsa_master_find_slave(struct net_device *dev,
>  	if (port < 0 || port >= ds->num_ports)
>  		return NULL;
>  
> -	return ds->ports[port].slave;
> +	slave_port = &ds->ports[port];
> +
> +	if (slave_port->type != DSA_PORT_TYPE_USER)

Can we optimize this with an unlikely()?

> +		return NULL;
> +
> +	return slave_port->slave;
>  }
>  
>  /* port.c */
> 


-- 
Florian