From: Jason Gunthorpe <jgg@mellanox.com>
Date: Sun, 29 Jul 2018 11:34:58 +0300
Subject: IB/ipoib: Do not remove child devices from within the ndo_uninit
Patch-mainline: v4.19-rc1
Git-commit: 25405d98a2aa0b9983bb9c36b0b00815d39394f4
References: bsc#1103992 FATE#326009

Switching to priv_destructor and needs_free_netdev created a subtle
ordering problem in ipoib_remove_one.

Now that unregister_netdev frees the netdev and priv we must ensure that
the children are unregistered before trying to unregister the parent,
or child unregister will use after free.

The solution is to unregister the children, then parent, in the same batch
all while holding the rtnl_lock. This closes all the races where a new
child could have been added and ensures proper ordering.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/ulp/ipoib/ipoib.h      |    7 +++++++
 drivers/infiniband/ulp/ipoib/ipoib_main.c |   28 +++++++++++++++++-----------
 drivers/infiniband/ulp/ipoib/ipoib_vlan.c |    6 ++++++
 3 files changed, 30 insertions(+), 11 deletions(-)

--- a/drivers/infiniband/ulp/ipoib/ipoib.h
+++ b/drivers/infiniband/ulp/ipoib/ipoib.h
@@ -330,6 +330,13 @@ struct ipoib_dev_priv {
 
 	unsigned long flags;
 
+	/*
+	 * This protects access to the child_intfs list.
+	 * To READ from child_intfs the RTNL or vlan_rwsem read side must be
+	 * held.  To WRITE RTNL and the vlan_rwsem write side must be held (in
+	 * that order) This lock exists because we have a few contexts where
+	 * we need the child_intfs, but do not want to grab the RTNL.
+	 */
 	struct rw_semaphore vlan_rwsem;
 	struct mutex mcast_mutex;
 
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -1937,18 +1937,15 @@ static int ipoib_ndo_init(struct net_dev
 
 static void ipoib_ndo_uninit(struct net_device *dev)
 {
-	struct ipoib_dev_priv *priv = ipoib_priv(dev), *cpriv, *tcpriv;
-	LIST_HEAD(head);
+	struct ipoib_dev_priv *priv = ipoib_priv(dev);
 
 	ASSERT_RTNL();
 
-	/* Delete any child interfaces first */
-	list_for_each_entry_safe(cpriv, tcpriv, &priv->child_intfs, list) {
-		/* Stop GC on child */
-		cancel_delayed_work_sync(&cpriv->neigh_reap_task);
-		unregister_netdevice_queue(cpriv->dev, &head);
-	}
-	unregister_netdevice_many(&head);
+	/*
+	 * ipoib_remove_one guarantees the children are removed before the
+	 * parent, and that is the only place where a parent can be removed.
+	 */
+	WARN_ON(!list_empty(&priv->child_intfs));
 
 	ipoib_neigh_hash_uninit(dev);
 
@@ -2464,16 +2461,25 @@ static void ipoib_add_one(struct ib_devi
 
 static void ipoib_remove_one(struct ib_device *device, void *client_data)
 {
-	struct ipoib_dev_priv *priv, *tmp;
+	struct ipoib_dev_priv *priv, *tmp, *cpriv, *tcpriv;
 	struct list_head *dev_list = client_data;
 
 	if (!dev_list)
 		return;
 
 	list_for_each_entry_safe(priv, tmp, dev_list, list) {
+		LIST_HEAD(head);
 		ipoib_parent_unregister_pre(priv->dev);
 
-		unregister_netdev(priv->dev);
+		rtnl_lock();
+
+		list_for_each_entry_safe(cpriv, tcpriv, &priv->child_intfs,
+					 list)
+			unregister_netdevice_queue(cpriv->dev, &head);
+		unregister_netdevice_queue(priv->dev, &head);
+		unregister_netdevice_many(&head);
+
+		rtnl_unlock();
 	}
 
 	kfree(dev_list);
--- a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
@@ -67,6 +67,12 @@ int __ipoib_vlan_add(struct ipoib_dev_pr
 
 	ASSERT_RTNL();
 
+	/*
+	 * Racing with unregister of the parent must be prevented by the
+	 * caller.
+	 */
+	WARN_ON(ppriv->dev->reg_state != NETREG_REGISTERED);
+
 	priv->parent = ppriv->dev;
 	priv->pkey = pkey;
 	priv->child_type = type;