bonding: Fix bonding crash

Following few steps will crash kernel -

  (a) Create bonding master
      > modprobe bonding miimon=50
  (b) Create macvlan bridge on eth2
      > ip link add link eth2 dev mvl0 address aa:0:0:0:0:01 \
	   type macvlan
  (c) Now try adding eth2 into the bond
      > echo +eth2 > /sys/class/net/bond0/bonding/slaves
      <crash>

Bonding does lots of things before checking if the device enslaved is
busy or not.

In this case when the notifier call-chain sends notifications, the
bond_netdev_event() assumes that the rx_handler /rx_handler_data is
registered while the bond_enslave() hasn't progressed far enough to
register rx_handler for the new slave.

This patch adds a rx_handler check that can be performed right at the
beginning of the enslave code to avoid getting into this situation.

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 217e8da..9599ed6 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1341,9 +1341,10 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
                            slave_dev->name);
        }
 
-       /* already enslaved */
-       if (slave_dev->flags & IFF_SLAVE) {
-               netdev_dbg(bond_dev, "Error: Device was already enslaved\n");
+       /* already in-use? */
+       if (netdev_is_rx_handler_busy(slave_dev)) {
+               netdev_err(bond_dev,
+                          "Error: Device is in use and cannot be enslaved\n");
                return -EBUSY;
        }
 

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3a788bf..e8d79d4 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3267,6 +3267,7 @@ static inline void napi_free_frags(struct napi_struct *napi)
        napi->skb = NULL;
 }
 
+bool netdev_is_rx_handler_busy(struct net_device *dev);
 int netdev_rx_handler_register(struct net_device *dev,
                               rx_handler_func_t *rx_handler,
                               void *rx_handler_data);

diff --git a/net/core/dev.c b/net/core/dev.c
index dd6ce59..ea63120 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3974,6 +3974,22 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
        return skb;
 }
 
+/**
+ *     netdev_is_rx_handler_busy - check if receive handler is registered
+ *     @dev: device to check
+ *
+ *     Check if a receive handler is already registered for a given device.
+ *     Return true if there one.
+ *
+ *     The caller must hold the rtnl_mutex.
+ */
+bool netdev_is_rx_handler_busy(struct net_device *dev)
+{
+       ASSERT_RTNL();
+       return dev && rtnl_dereference(dev->rx_handler);
+}
+EXPORT_SYMBOL_GPL(netdev_is_rx_handler_busy);
+
 /**
  *     netdev_rx_handler_register - register receive handler
  *     @dev: device to register a handler for