This is a note to let you know that I've just added the patch titled
bridge: use spin_lock_bh() in br_multicast_set_hash_max
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bridge-use-spin_lock_bh-in-br_multicast_set_hash_max.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From foo@baz Mon Jan 13 09:44:41 PST 2014
From: Curt Brune <[email protected]>
Date: Mon, 6 Jan 2014 11:00:32 -0800
Subject: bridge: use spin_lock_bh() in br_multicast_set_hash_max
From: Curt Brune <[email protected]>
[ 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 <[email protected]>
Signed-off-by: Scott Feldman <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/bridge/br_multicast.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -2004,7 +2004,7 @@ int br_multicast_set_hash_max(struct net
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;
@@ -2036,7 +2036,7 @@ rollback:
}
unlock:
- spin_unlock(&br->multicast_lock);
+ spin_unlock_bh(&br->multicast_lock);
return err;
}
Patches currently in stable-queue which might be from [email protected]
are
queue-3.12/bridge-use-spin_lock_bh-in-br_multicast_set_hash_max.patch
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