| Message ID | 20140106190032.10912.1521.stgit@monster-03.cumulusnetworks.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, Jan 6, 2014 at 11:00 AM, Scott Feldman <sfeldma@cumulusnetworks.com> wrote: > From: Curt Brune <curt@cumulusnetworks.com> > > 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 > I think this should probably go to net instead of net-next, and -stable too. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Cong Wang <cwang@twopensource.com> Date: Mon, 6 Jan 2014 11:11:45 -0800 > On Mon, Jan 6, 2014 at 11:00 AM, Scott Feldman > <sfeldma@cumulusnetworks.com> wrote: >> From: Curt Brune <curt@cumulusnetworks.com> >> >> 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 >> > > > I think this should probably go to net instead of net-next, > and -stable too. Agreed, applied to 'net' and queued up for -stable. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index 4c214b2..ef66365 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: } unlock: - spin_unlock(&br->multicast_lock); + spin_unlock_bh(&br->multicast_lock); return err; }