Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 36/62] bridge: use spin_lock_bh() in br_multicast_set_hash_max | Date | Mon, 13 Jan 2014 16:27:01 -0800 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Curt Brune <curt@cumulusnetworks.com>
[ 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@cumulusnetworks.com> Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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 @@ -1839,7 +1839,7 @@ 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; @@ -1871,7 +1871,7 @@ rollback: } unlock: - spin_unlock(&br->multicast_lock); + spin_unlock_bh(&br->multicast_lock); return err; }
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