linux-kernel - [PATCH 3.16 034/212] IB/ipoib: Fix deadlock over vlan

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Message-ID: <lsq.1496331795.444566936@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:43:15 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Erez Shitrit" <erezsh@...lanox.com>,
        "Alex Vesker" <valex@...lanox.com>,
        "Doug Ledford" <dledford@...hat.com>,
        "Feras Daoud" <ferasda@...lanox.com>,
        "Leon Romanovsky" <leon@...nel.org>
Subject: [PATCH 3.16 034/212] IB/ipoib: Fix deadlock over vlan_mutex

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Feras Daoud <ferasda@...lanox.com>

commit 1c3098cdb05207e740715857df7b0998e372f527 upstream.

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.

Fixes: cbbe1efa4972 ("IPoIB: Fix deadlock between ipoib_open() and child interface create")
Signed-off-by: Feras Daoud <ferasda@...lanox.com>
Signed-off-by: Erez Shitrit <erezsh@...lanox.com>
Reviewed-by: Alex Vesker <valex@...lanox.com>
Signed-off-by: Leon Romanovsky <leon@...nel.org>
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/infiniband/ulp/ipoib/ipoib_vlan.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
@@ -196,7 +196,6 @@ 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;
@@ -204,6 +203,11 @@ 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) {