From b19cbe2a1695c09c74f83646c4b82b51123b3690 Mon Sep 17 00:00:00 2001 From: Patrick McHardy <kaber@trash.net> Date: Thu, 22 Mar 2007 12:25:20 -0700 Subject: [PATCH] [BRIDGE]: Fix fdb RCU race br_fdb_get use atomic_inc to increase the refcount of an element found on a RCU protected list, which can lead to the following race: CPU0 CPU1 br_fdb_get: rcu_read_lock __br_fdb_get: find element fdb_delete: hlist_del_rcu br_fdb_put br_fdb_put: atomic_dec_and_test call_rcu(fdb_rcu_free) br_fdb_get: atomic_inc rcu_read_unlock fdb_rcu_free: kmem_cache_free Use atomic_inc_not_zero instead. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net> --- net/bridge/br_fdb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c index def2e403f932..8d566c13cc73 100644 --- a/net/bridge/br_fdb.c +++ b/net/bridge/br_fdb.c @@ -197,8 +197,8 @@ struct net_bridge_fdb_entry *br_fdb_get(struct net_bridge *br, rcu_read_lock(); fdb = __br_fdb_get(br, addr); - if (fdb) - atomic_inc(&fdb->use_count); + if (fdb && !atomic_inc_not_zero(&fdb->use_count)) + fdb = NULL; rcu_read_unlock(); return fdb; }