net sched: fix race in mirred device removal

This fixes hang when target device of mirred packet classifier
action is removed.

If a mirror or redirection action is configured to cause packets
to go to another device, the classifier holds a ref count, but was assuming
the adminstrator cleaned up all redirections before removing. The fix
is to add a notifier and cleanup during unregister.

The new list is implicitly protected by RTNL mutex because
it is held during filter add/delete as well as notifier.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 41 insertions, 3 deletions

diff --git a/include/net/tc_act/tc_mirred.h b/include/net/tc_act/tc_mirred.h
index ceac661cdfd..cfe2943690f 100644
--- a/include/net/tc_act/tc_mirred.h
+++ b/include/net/tc_act/tc_mirred.h
@@ -9,6 +9,7 @@ struct tcf_mirred {
         int                     tcfm_ifindex;
         int                     tcfm_ok_push;
         struct net_device       *tcfm_dev;
+        struct list_head        tcfm_list;
 };
 #define to_mirred(pc) \
         container_of(pc, struct tcf_mirred, common)
diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index c0b6863e3b8..1980b71c283 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -33,6 +33,7 @@
 static struct tcf_common *tcf_mirred_ht[MIRRED_TAB_MASK + 1];
 static u32 mirred_idx_gen;
 static DEFINE_RWLOCK(mirred_lock);
+static LIST_HEAD(mirred_list);
 
 static struct tcf_hashinfo mirred_hash_info = {
         .htab   =       tcf_mirred_ht,
@@ -47,7 +48,9 @@ static inline int tcf_mirred_release(struct tcf_mirred *m, int bind)
                         m->tcf_bindcnt--;
                 m->tcf_refcnt--;
                 if(!m->tcf_bindcnt && m->tcf_refcnt <= 0) {
-                        dev_put(m->tcfm_dev);
+                        list_del(&m->tcfm_list);
+                        if (m->tcfm_dev)
+                                dev_put(m->tcfm_dev);
                         tcf_hash_destroy(&m->common, &mirred_hash_info);
                         return 1;
                 }
@@ -134,8 +137,10 @@ static int tcf_mirred_init(struct nlattr *nla, struct nlattr *est,
                 m->tcfm_ok_push = ok_push;
         }
         spin_unlock_bh(&m->tcf_lock);
-        if (ret == ACT_P_CREATED)
+        if (ret == ACT_P_CREATED) {
+                list_add(&m->tcfm_list, &mirred_list);
                 tcf_hash_insert(pc, &mirred_hash_info);
+        }
 
         return ret;
 }
@@ -162,9 +167,14 @@ static int tcf_mirred(struct sk_buff *skb, struct tc_action *a,
         m->tcf_tm.lastuse = jiffies;
 
         dev = m->tcfm_dev;
+        if (!dev) {
+                printk_once(KERN_NOTICE "tc mirred: target device is gone\n");
+                goto out;
+        }
+
         if (!(dev->flags & IFF_UP)) {
                 if (net_ratelimit())
-                        pr_notice("tc mirred to Houston: device %s is gone!\n",
+                        pr_notice("tc mirred to Houston: device %s is down\n",
                                   dev->name);
                 goto out;
         }
@@ -232,6 +242,28 @@ nla_put_failure:
         return -1;
 }
 
+static int mirred_device_event(struct notifier_block *unused,
+                               unsigned long event, void *ptr)
+{
+        struct net_device *dev = ptr;
+        struct tcf_mirred *m;
+
+        if (event == NETDEV_UNREGISTER)
+                list_for_each_entry(m, &mirred_list, tcfm_list) {
+                        if (m->tcfm_dev == dev) {
+                                dev_put(dev);
+                                m->tcfm_dev = NULL;
+                        }
+                }
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block mirred_device_notifier = {
+        .notifier_call = mirred_device_event,
+};
+
+
 static struct tc_action_ops act_mirred_ops = {
         .kind           =       "mirred",
         .hinfo          =       &mirred_hash_info,
@@ -252,12 +284,17 @@ MODULE_LICENSE("GPL");
 
 static int __init mirred_init_module(void)
 {
+        int err = register_netdevice_notifier(&mirred_device_notifier);
+        if (err)
+                return err;
+
         pr_info("Mirror/redirect action on\n");
         return tcf_register_action(&act_mirred_ops);
 }
 
 static void __exit mirred_cleanup_module(void)
 {
+        unregister_netdevice_notifier(&mirred_device_notifier);
         tcf_unregister_action(&act_mirred_ops);
 }