net: dsa: Do not leave DSA master with NULL netdev_ops

[ Upstream commit 050569fc8384c8056bacefcc246bcb2dfe574936 ]

When ndo_get_phys_port_name() for the CPU port was added we introduced
an early check for when the DSA master network device in
dsa_master_ndo_setup() already implements ndo_get_phys_port_name(). When
we perform the teardown operation in dsa_master_ndo_teardown() we would
not be checking that cpu_dp->orig_ndo_ops was successfully allocated and
non-NULL initialized.

With network device drivers such as virtio_net, this leads to a NPD as
soon as the DSA switch hanging off of it gets torn down because we are
now assigning the virtio_net device's netdev_ops a NULL pointer.

Fixes: da7b9e9b00d4 ("net: dsa: Add ndo_get_phys_port_name() for CPU port")
Reported-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/dsa/master.c b/net/dsa/master.c
index 3255dfc..be0b4ed 100644 (file)
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -259,7 +259,8 @@ static void dsa_master_ndo_teardown(struct net_device *dev)
 {
        struct dsa_port *cpu_dp = dev->dsa_ptr;
 
-       dev->netdev_ops = cpu_dp->orig_ndo_ops;
+       if (cpu_dp->orig_ndo_ops)
+               dev->netdev_ops = cpu_dp->orig_ndo_ops;
        cpu_dp->orig_ndo_ops = NULL;
 }