3.9-stable review patch.  If anyone has any objections, please let me know.

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


From: stephen hemminger <[email protected]>

[ 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 <[email protected]>
Signed-off-by: Stephen Hemminger <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 net/bridge/br_stp_timer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/bridge/br_stp_timer.c
+++ b/net/bridge/br_stp_timer.c
@@ -107,7 +107,7 @@ static void br_tcn_timer_expired(unsigne
 
        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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