linux-kernel - [83/94] bridge: fix race with topology change timer

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Date:	Tue, 28 May 2013 04:49:53 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "JerryKang" <jerry.kang@...sung.com>,
	"stephen hemminger" <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [83/94] bridge: fix race with topology change timer

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

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

From: stephen hemminger <stephen@...workplumber.org>

[ 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@...sung.com>
Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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 58de2a0..c83ee79 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);

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