diff options
authorCurt Brune <curt@cumulusnetworks.com>2014-01-06 11:00:32 -0800
committerDavid S. Miller <davem@davemloft.net>2014-01-06 16:39:47 -0500
commitfe0d692bbc645786bce1a98439e548ae619269f5 (patch)
parent88ad31491e21f5dec347911d9804c673af414a09 (diff)
bridge: use spin_lock_bh() in br_multicast_set_hash_max
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@cumulusnetworks.com> Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 files changed, 2 insertions, 2 deletions
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 4c214b2b88ef..ef66365b7354 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1998,7 +1998,7 @@ 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;
@@ -2030,7 +2030,7 @@ rollback:
- spin_unlock(&br->multicast_lock);
+ spin_unlock_bh(&br->multicast_lock);
return err;

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