veth: prevent oops caused by netdev destructor

From: Stephen Hemminger <shemminger@vyatta.com>

The veth driver will oops if sysfs hooks are open while module is removed.

The net device destructor can not point to code in a module; basically
there are only two possible safe values: NULL - no destructor, or
free_netdev - free on last use

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 015db1c..8e56fcf 100644 (file)
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -210,14 +210,11 @@ rx_drop:
 
 static struct net_device_stats *veth_get_stats(struct net_device *dev)
 {
-       struct veth_priv *priv;
-       struct net_device_stats *dev_stats;
-       int cpu;
+       struct veth_priv *priv = netdev_priv(dev);
+       struct net_device_stats *dev_stats = &dev->stats;
+       unsigned int cpu;
        struct veth_net_stats *stats;
 
-       priv = netdev_priv(dev);
-       dev_stats = &dev->stats;
-
        dev_stats->rx_packets = 0;
        dev_stats->tx_packets = 0;
        dev_stats->rx_bytes = 0;
@@ -225,16 +222,17 @@ static struct net_device_stats *veth_get_stats(struct net_device *dev)
        dev_stats->tx_dropped = 0;
        dev_stats->rx_dropped = 0;
 
-       for_each_online_cpu(cpu) {
-               stats = per_cpu_ptr(priv->stats, cpu);
+       if (priv->stats)
+               for_each_online_cpu(cpu) {
+                       stats = per_cpu_ptr(priv->stats, cpu);
 
-               dev_stats->rx_packets += stats->rx_packets;
-               dev_stats->tx_packets += stats->tx_packets;
-               dev_stats->rx_bytes += stats->rx_bytes;
-               dev_stats->tx_bytes += stats->tx_bytes;
-               dev_stats->tx_dropped += stats->tx_dropped;
-               dev_stats->rx_dropped += stats->rx_dropped;
-       }
+                       dev_stats->rx_packets += stats->rx_packets;
+                       dev_stats->tx_packets += stats->tx_packets;
+                       dev_stats->rx_bytes += stats->rx_bytes;
+                       dev_stats->tx_bytes += stats->tx_bytes;
+                       dev_stats->tx_dropped += stats->tx_dropped;
+                       dev_stats->rx_dropped += stats->rx_dropped;
+               }
 
        return dev_stats;
 }
@@ -261,6 +259,8 @@ static int veth_close(struct net_device *dev)
        netif_carrier_off(dev);
        netif_carrier_off(priv->peer);
 
+       free_percpu(priv->stats);
+       priv->stats = NULL;
        return 0;
 }
 
@@ -291,15 +291,6 @@ static int veth_dev_init(struct net_device *dev)
        return 0;
 }
 
-static void veth_dev_free(struct net_device *dev)
-{
-       struct veth_priv *priv;
-
-       priv = netdev_priv(dev);
-       free_percpu(priv->stats);
-       free_netdev(dev);
-}
-
 static const struct net_device_ops veth_netdev_ops = {
        .ndo_init            = veth_dev_init,
        .ndo_open            = veth_open,
@@ -317,7 +308,7 @@ static void veth_setup(struct net_device *dev)
        dev->netdev_ops = &veth_netdev_ops;
        dev->ethtool_ops = &veth_ethtool_ops;
        dev->features |= NETIF_F_LLTX;
-       dev->destructor = veth_dev_free;
+       dev->destructor = free_netdev;
 }
 
 /*