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@samsung.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/bridge/br_stp_timer.c b/net/bridge/br_stp_timer.c
index c3530a81a33bf40c9162cb28a6f931ea937baf54..950663d4d3303327e9dcf6d383069734af441a44 100644 (file)
--- 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);