After commit 1ce87720d456 ("net: sched: make cls_u32 lockless")
we began to release tc actions in a RCU callback. However,
mirred action relies on RTNL lock to protect the global
mirred_list, therefore we could have a race condition
between RCU callback and netdevice event, which caused
a list corruption as reported by Vinson.Instead of relying on RTNL lock, introduce a spinlock to protect this list. Note, in non-bind case, it is still called with RTNL lock, therefore should disable BH too. Reported-by: Vinson Lee <[email protected]> Cc: John Fastabend <[email protected]> Cc: Jamal Hadi Salim <[email protected]> Signed-off-by: Cong Wang <[email protected]> Signed-off-by: Cong Wang <[email protected]> --- net/sched/act_mirred.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c index 2d1be4a..3e7c51a 100644 --- a/net/sched/act_mirred.c +++ b/net/sched/act_mirred.c @@ -31,13 +31,17 @@ #define MIRRED_TAB_MASK 7 static LIST_HEAD(mirred_list); +static DEFINE_SPINLOCK(mirred_list_lock); static void tcf_mirred_release(struct tc_action *a, int bind) { struct tcf_mirred *m = to_mirred(a); struct net_device *dev = rcu_dereference_protected(m->tcfm_dev, 1); + /* We could be called either in a RCU callback or with RTNL lock held. */ + spin_lock_bh(&mirred_list_lock); list_del(&m->tcfm_list); + spin_unlock_bh(&mirred_list_lock); if (dev) dev_put(dev); } @@ -123,7 +127,9 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla, } if (ret == ACT_P_CREATED) { + spin_lock_bh(&mirred_list_lock); list_add(&m->tcfm_list, &mirred_list); + spin_unlock_bh(&mirred_list_lock); tcf_hash_insert(a); } @@ -221,7 +227,8 @@ static int mirred_device_event(struct notifier_block *unused, struct tcf_mirred *m; ASSERT_RTNL(); - if (event == NETDEV_UNREGISTER) + if (event == NETDEV_UNREGISTER) { + spin_lock_bh(&mirred_list_lock); list_for_each_entry(m, &mirred_list, tcfm_list) { if (rcu_access_pointer(m->tcfm_dev) == dev) { dev_put(dev); @@ -231,6 +238,8 @@ static int mirred_device_event(struct notifier_block *unused, RCU_INIT_POINTER(m->tcfm_dev, NULL); } } + spin_unlock_bh(&mirred_list_lock); + } return NOTIFY_DONE; } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
