net: dsa: Discard frames from unused ports

BugLink: http://bugs.launchpad.net/bugs/1763366
[ Upstream commit fc5f33768cca7144f8d793205b229d46740d183b ]

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@gmail.com>
Fixes: 91da11f870f0 ("net: Distributed Switch Architecture protocol support")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 7d036696e8c47bde0c6a8e5827a451acb376ccb9..65292b9fa01a509f263ccf082a45315213ae86d0 100644 (file)
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -117,6 +117,7 @@ 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;
@@ -128,7 +129,12 @@ 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 (unlikely(slave_port->type != DSA_PORT_TYPE_USER))
+               return NULL;
+
+       return slave_port->slave;
 }
 
 /* port.c */