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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mahesh Bandewar <maheshb@google.com>,
        Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 32/73] bonding: Fix bonding crash
Date: Wed, 28 Sep 2016 11:05:02 +0200
Message-Id: <20160928090437.009126874@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mahesh Bandewar <maheshb@google.com>


[ 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@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/bonding/bond_main.c |    7 ++++---
 include/linux/netdevice.h       |    1 +
 net/core/dev.c                  |   16 ++++++++++++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1317,9 +1317,10 @@ int bond_enslave(struct net_device *bond
 			    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;
 	}
 
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3036,6 +3036,7 @@ static inline void napi_free_frags(struc
 	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);
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3722,6 +3722,22 @@ static inline struct sk_buff *handle_ing
 }
 
 /**
+ *	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