[ 3.8.y.z extended stable ] Patch "bridge: fix race with topology change timer" 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: fix race with topology change timer

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From e42056419e11756ea979e538704bc1529cddfdfb Mon Sep 17 00:00:00 2001
From: stephen hemminger <stephen at networkplumber.org>
Date: Thu, 2 May 2013 14:23:28 +0000
Subject: bridge: fix race with topology change timer

[ Upstream commit 83401eb4990ff6af55aeed8f49681558544192e6 ]

A bridge should only send topology change notice if it is not
the root bridge. It is possible for message age timer to elect itself
as a new root bridge, and still have a topology change timer running
but waiting for bridge lock on other CPU.

Solve the race by checking if we are root bridge before continuing.
This was the root cause of the cases where br_send_tcn_bpdu would OOPS.

Reported-by: JerryKang <jerry.kang at samsung.com>
Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/bridge/br_stp_timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_stp_timer.c b/net/bridge/br_stp_timer.c
index c3530a8..950663d 100644
--- a/net/bridge/br_stp_timer.c
+++ b/net/bridge/br_stp_timer.c
@@ -107,7 +107,7 @@ static void br_tcn_timer_expired(unsigned long arg)

 	br_debug(br, "tcn timer expired\n");
 	spin_lock(&br->lock);
-	if (br->dev->flags & IFF_UP) {
+	if (!br_is_root_bridge(br) && (br->dev->flags & IFF_UP)) {
 		br_transmit_tcn(br);

 		mod_timer(&br->tcn_timer,jiffies + br->bridge_hello_time);
--
1.8.1.2