[3.19.y-ckt stable] Patch "bridge: netlink: fix slave_changelink/br_setport race conditions" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    bridge: netlink: fix slave_changelink/br_setport race conditions

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From d4edf0d60bf08b93998f5e3b7004f804defeb154 Mon Sep 17 00:00:00 2001
From: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Date: Wed, 22 Jul 2015 13:03:40 +0200
Subject: bridge: netlink: fix slave_changelink/br_setport race conditions

commit 963ad94853000ab100f5ff19eea80095660d41b4 upstream.

Since slave_changelink support was added there have been a few race
conditions when using br_setport() since some of the port functions it
uses require the bridge lock. It is very easy to trigger a lockup due to
some internal spin_lock() usage without bh disabled, also it's possible to
get the bridge into an inconsistent state.

Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Fixes: 3ac636b8591c ("bridge: implement rtnl_link_ops->slave_changelink")
Reviewed-by: Jiri Pirko <jiri at resnulli.us>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/bridge/br_netlink.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 9f5eb55..36e56a9 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -466,9 +466,17 @@ static int br_port_slave_changelink(struct net_device *brdev,
 				    struct nlattr *tb[],
 				    struct nlattr *data[])
 {
+	struct net_bridge *br = netdev_priv(brdev);
+	int ret;
+
 	if (!data)
 		return 0;
-	return br_setport(br_port_get_rtnl(dev), data);
+
+	spin_lock_bh(&br->lock);
+	ret = br_setport(br_port_get_rtnl(dev), data);
+	spin_unlock_bh(&br->lock);
+
+	return ret;
 }

 static int br_port_fill_slave_info(struct sk_buff *skb,
--
1.9.1