[PATCH 3.12 053/119] bonding: Fix bonding crash

[Jiri Slaby]

From: Mahesh Bandewar <maheshb@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit 24b27fc4cdf9e10c5e79e5923b6b7c2c5c95096c ]

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@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/net/bonding/bond_main.c |  7 ++++---
 include/linux/netdevice.h       |  1 +
 net/core/dev.c                  | 16 ++++++++++++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 5dcac318e317..3a9b876c419c 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1291,9 +1291,10 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 			   bond_dev->name, slave_dev->name);
 	}
 
-	/* already enslaved */
-	if (slave_dev->flags & IFF_SLAVE) {
-		pr_debug("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 51bfd7a68272..41239f739d51 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2367,6 +2367,7 @@ static inline void napi_free_frags(struct napi_struct *napi)
 	napi->skb = NULL;
 }
 
+bool netdev_is_rx_handler_busy(struct net_device *dev);
 extern 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 f991f5d3371d..d30c12263f38 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3424,6 +3424,22 @@ out:
 #endif
 
 /**
+ *	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
  *	@rx_handler: receive handler to register
-- 
2.10.0