switchdev: Require RTNL mutex to be held when sending FDB notifications

When switchdev drivers process FDB notifications from the underlying
device they resolve the netdev to which the entry points to and notify
the bridge using the switchdev notifier.

However, since the RTNL mutex is not held there is nothing preventing
the netdev from disappearing in the middle, which will cause
br_switchdev_event() to dereference a non-existing netdev.

Make switchdev drivers hold the lock at the beginning of the
notification processing session and release it once it ends, after
notifying the bridge.

Also, remove switchdev_mutex and fdb_lock, as they are no longer needed
when RTNL mutex is held.

Fixes: 03bf0c281234 ("switchdev: introduce switchdev notifier")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 7 deletions

diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index ebc661d3b6e3..47f7da58a7f0 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -20,6 +20,7 @@
 #include <linux/list.h>
 #include <linux/workqueue.h>
 #include <linux/if_vlan.h>
+#include <linux/rtnetlink.h>
 #include <net/ip_fib.h>
 #include <net/switchdev.h>
 
@@ -567,7 +568,6 @@ int switchdev_port_obj_dump(struct net_device *dev, struct switchdev_obj *obj,
 }
 EXPORT_SYMBOL_GPL(switchdev_port_obj_dump);
 
-static DEFINE_MUTEX(switchdev_mutex);
 static RAW_NOTIFIER_HEAD(switchdev_notif_chain);
 
 /**
@@ -582,9 +582,9 @@ int register_switchdev_notifier(struct notifier_block *nb)
 {
 	int err;
 
-	mutex_lock(&switchdev_mutex);
+	rtnl_lock();
 	err = raw_notifier_chain_register(&switchdev_notif_chain, nb);
-	mutex_unlock(&switchdev_mutex);
+	rtnl_unlock();
 	return err;
 }
 EXPORT_SYMBOL_GPL(register_switchdev_notifier);
@@ -600,9 +600,9 @@ int unregister_switchdev_notifier(struct notifier_block *nb)
 {
 	int err;
 
-	mutex_lock(&switchdev_mutex);
+	rtnl_lock();
 	err = raw_notifier_chain_unregister(&switchdev_notif_chain, nb);
-	mutex_unlock(&switchdev_mutex);
+	rtnl_unlock();
 	return err;
 }
 EXPORT_SYMBOL_GPL(unregister_switchdev_notifier);
@@ -616,16 +616,17 @@ EXPORT_SYMBOL_GPL(unregister_switchdev_notifier);
  *	Call all network notifier blocks. This should be called by driver
  *	when it needs to propagate hardware event.
  *	Return values are same as for atomic_notifier_call_chain().
+ *	rtnl_lock must be held.
  */
 int call_switchdev_notifiers(unsigned long val, struct net_device *dev,
 			     struct switchdev_notifier_info *info)
 {
 	int err;
 
+	ASSERT_RTNL();
+
 	info->dev = dev;
-	mutex_lock(&switchdev_mutex);
 	err = raw_notifier_call_chain(&switchdev_notif_chain, val, info);
-	mutex_unlock(&switchdev_mutex);
 	return err;
 }
 EXPORT_SYMBOL_GPL(call_switchdev_notifiers);