Commit fe0d692bbc645786bce1a98439e548ae619269f5
Committed by
David S. Miller
1 parent
88ad31491e
Exists in
master
and in
16 other branches
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>
Showing 1 changed file with 2 additions and 2 deletions Side-by-side Diff
net/bridge/br_multicast.c
... | ... | @@ -1998,7 +1998,7 @@ |
1998 | 1998 | u32 old; |
1999 | 1999 | struct net_bridge_mdb_htable *mdb; |
2000 | 2000 | |
2001 | - spin_lock(&br->multicast_lock); | |
2001 | + spin_lock_bh(&br->multicast_lock); | |
2002 | 2002 | if (!netif_running(br->dev)) |
2003 | 2003 | goto unlock; |
2004 | 2004 | |
... | ... | @@ -2030,7 +2030,7 @@ |
2030 | 2030 | } |
2031 | 2031 | |
2032 | 2032 | unlock: |
2033 | - spin_unlock(&br->multicast_lock); | |
2033 | + spin_unlock_bh(&br->multicast_lock); | |
2034 | 2034 | |
2035 | 2035 | return err; |
2036 | 2036 | } |