3.2.55-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Curt Brune <curt@xxxxxxxxxxxxxxxxxxx> [ Upstream commit fe0d692bbc645786bce1a98439e548ae619269f5 ] br_multicast_set_hash_max() is called from process context in net/bridge/br_sysfs_br.c by the sysfs store_hash_max() function. br_multicast_set_hash_max() calls spin_lock(&br->multicast_lock), which can deadlock the CPU if a softirq that also tries to take the same lock interrupts br_multicast_set_hash_max() while the lock is held . This can happen quite easily when any of the bridge multicast timers expire, which try to take the same lock. The fix here is to use spin_lock_bh(), preventing other softirqs from executing on this CPU. Steps to reproduce: 1. Create a bridge with several interfaces (I used 4). 2. Set the "multicast query interval" to a low number, like 2. 3. Enable the bridge as a multicast querier. 4. Repeatedly set the bridge hash_max parameter via sysfs. # brctl addbr br0 # brctl addif br0 eth1 eth2 eth3 eth4 # brctl setmcqi br0 2 # brctl setmcquerier br0 1 # while true ; do echo 4096 > /sys/class/net/br0/bridge/hash_max; done Signed-off-by: Curt Brune <curt@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Scott Feldman <sfeldma@xxxxxxxxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- net/bridge/br_multicast.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index a06deca..2157984 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -1743,7 +1743,7 @@ int br_multicast_set_hash_max(struct net_bridge *br, unsigned long val) u32 old; struct net_bridge_mdb_htable *mdb; - spin_lock(&br->multicast_lock); + spin_lock_bh(&br->multicast_lock); if (!netif_running(br->dev)) goto unlock; @@ -1775,7 +1775,7 @@ rollback: } unlock: - spin_unlock(&br->multicast_lock); + spin_unlock_bh(&br->multicast_lock); return err; } -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html