Patch "IB/ipoib: Fix deadlock over vlan_mutex" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

IB/ipoib: Fix deadlock over vlan_mutex

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-ipoib-fix-deadlock-over-vlan_mutex.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Feras Daoud <[email protected]>
Date: Wed, 28 Dec 2016 14:47:22 +0200
Subject: IB/ipoib: Fix deadlock over vlan_mutex

From: Feras Daoud <[email protected]>

[ Upstream commit 1c3098cdb05207e740715857df7b0998e372f527 ]

This patch fixes Deadlock while executing ipoib_vlan_delete.

The function takes the vlan_rwsem semaphore and calls unregister_netdevice. The later function calls ipoib_mcast_stop_thread that cause workqueue flush.

When the queue has one of the ipoib_ib_dev_flush_xxx events, a deadlock occur because these events also tries to catch the same vlan_rwsem semaphore.

To fix, unregister_netdevice should be called after releasing the semaphore.

---
 drivers/infiniband/ulp/ipoib/ipoib_vlan.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -185,7 +185,6 @@ int ipoib_vlan_delete(struct net_device
 	list_for_each_entry_safe(priv, tpriv, &ppriv->child_intfs, list) {
 		if (priv->pkey == pkey &&
 		    priv->child_type == IPOIB_LEGACY_CHILD) {
-			unregister_netdevice(priv->dev);
 			list_del(&priv->list);
 			dev = priv->dev;
 			break;

@@ -193,6 +192,11 @@ int ipoib_vlan_delete(struct net_device
 	}
 	up_write(&ppriv->vlan_rwsem);
 
+	if (dev) {
+		ipoib_dbg(ppriv, "delete child vlan %s\n", dev->name);
+		unregister_netdevice(dev);
+	}
+
 	rtnl_unlock();
 
 	if (dev) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/ib-ipoib-replace-list_del-of-the-neigh-list-with-list_del_init.patch queue-4.4/ib-ipoib-rtnl_unlock-can-not-come-after-free_netdev.patch queue-4.4/ib-ipoib-fix-deadlock-over-vlan_mutex.patch