mac80211: add ieee80211_iterate_active_interfaces_rtnl()

If it is needed to disconnect multiple virtual interfaces after
(WoWLAN-) suspend, the most obvious approach would be to iterate
all interfaces by calling ieee80211_iterate_active_interfaces()
and then call ieee80211_resume_disconnect() for each one. This
is what the iwlmvm driver does.

Unfortunately, this causes a locking dependency from mac80211's
iflist_mtx to the key_mtx. This is problematic as the former is
intentionally never held while calling any driver operation to
allow drivers to iterate with their own locks held. The key_mtx
is held while installing a key into the driver though, so this
new lock dependency means drivers implementing the logic above
can no longer hold their own lock while iterating.

To fix this, add a new ieee80211_iterate_active_interfaces_rtnl()
function that iterates while the RTNL is already held. This is
true during suspend/resume, so that then the locking dependency
isn't introduced.

While at it, also refactor the various interface iterators and
keep only a single implementation called by the various cases.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 53 insertions, 37 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index cc6035f1a2f1..3411c59b636b 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -3920,6 +3920,25 @@ void ieee80211_iterate_active_interfaces_atomic(struct ieee80211_hw *hw,
                                                 void *data);
 
 /**
+ * ieee80211_iterate_active_interfaces_rtnl - iterate active interfaces
+ *
+ * This function iterates over the interfaces associated with a given
+ * hardware that are currently active and calls the callback for them.
+ * This version can only be used while holding the RTNL.
+ *
+ * @hw: the hardware struct of which the interfaces should be iterated over
+ * @iter_flags: iteration flags, see &enum ieee80211_interface_iteration_flags
+ * @iterator: the iterator function to call, cannot sleep
+ * @data: first argument of the iterator function
+ */
+void ieee80211_iterate_active_interfaces_rtnl(struct ieee80211_hw *hw,
+                                              u32 iter_flags,
+                                              void (*iterator)(void *data,
+                                                u8 *mac,
+                                                struct ieee80211_vif *vif),
+                                              void *data);
+
+/**
  * ieee80211_queue_work - add work onto the mac80211 workqueue
  *
  * Drivers and mac80211 use this to add work onto the mac80211 workqueue.
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index e1b34a18b243..75a16853fb45 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -567,18 +567,15 @@ void ieee80211_flush_queues(struct ieee80211_local *local,
                                         IEEE80211_QUEUE_STOP_REASON_FLUSH);
 }
 
-void ieee80211_iterate_active_interfaces(
-        struct ieee80211_hw *hw, u32 iter_flags,
-        void (*iterator)(void *data, u8 *mac,
-                         struct ieee80211_vif *vif),
-        void *data)
+static void __iterate_active_interfaces(struct ieee80211_local *local,
+                                        u32 iter_flags,
+                                        void (*iterator)(void *data, u8 *mac,
+                                                struct ieee80211_vif *vif),
+                                        void *data)
 {
-        struct ieee80211_local *local = hw_to_local(hw);
         struct ieee80211_sub_if_data *sdata;
 
-        mutex_lock(&local->iflist_mtx);
-
-        list_for_each_entry(sdata, &local->interfaces, list) {
+        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
                 switch (sdata->vif.type) {
                 case NL80211_IFTYPE_MONITOR:
                         if (!(sdata->u.mntr_flags & MONITOR_FLAG_ACTIVE))
@@ -597,13 +594,25 @@ void ieee80211_iterate_active_interfaces(
                                  &sdata->vif);
         }
 
-        sdata = rcu_dereference_protected(local->monitor_sdata,
-                                          lockdep_is_held(&local->iflist_mtx));
+        sdata = rcu_dereference_check(local->monitor_sdata,
+                                      lockdep_is_held(&local->iflist_mtx) ||
+                                      lockdep_rtnl_is_held());
         if (sdata &&
             (iter_flags & IEEE80211_IFACE_ITER_RESUME_ALL ||
              sdata->flags & IEEE80211_SDATA_IN_DRIVER))
                 iterator(data, sdata->vif.addr, &sdata->vif);
+}
 
+void ieee80211_iterate_active_interfaces(
+        struct ieee80211_hw *hw, u32 iter_flags,
+        void (*iterator)(void *data, u8 *mac,
+                         struct ieee80211_vif *vif),
+        void *data)
+{
+        struct ieee80211_local *local = hw_to_local(hw);
+
+        mutex_lock(&local->iflist_mtx);
+        __iterate_active_interfaces(local, iter_flags, iterator, data);
         mutex_unlock(&local->iflist_mtx);
 }
 EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces);
@@ -615,38 +624,26 @@ void ieee80211_iterate_active_interfaces_atomic(
         void *data)
 {
         struct ieee80211_local *local = hw_to_local(hw);
-        struct ieee80211_sub_if_data *sdata;
 
         rcu_read_lock();
+        __iterate_active_interfaces(local, iter_flags, iterator, data);
+        rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_atomic);
 
-        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
-                switch (sdata->vif.type) {
-                case NL80211_IFTYPE_MONITOR:
-                        if (!(sdata->u.mntr_flags & MONITOR_FLAG_ACTIVE))
-                                continue;
-                        break;
-                case NL80211_IFTYPE_AP_VLAN:
-                        continue;
-                default:
-                        break;
-                }
-                if (!(iter_flags & IEEE80211_IFACE_ITER_RESUME_ALL) &&
-                    !(sdata->flags & IEEE80211_SDATA_IN_DRIVER))
-                        continue;
-                if (ieee80211_sdata_running(sdata))
-                        iterator(data, sdata->vif.addr,
-                                 &sdata->vif);
-        }
+void ieee80211_iterate_active_interfaces_rtnl(
+        struct ieee80211_hw *hw, u32 iter_flags,
+        void (*iterator)(void *data, u8 *mac,
+                         struct ieee80211_vif *vif),
+        void *data)
+{
+        struct ieee80211_local *local = hw_to_local(hw);
 
-        sdata = rcu_dereference(local->monitor_sdata);
-        if (sdata &&
-            (iter_flags & IEEE80211_IFACE_ITER_RESUME_ALL ||
-             sdata->flags & IEEE80211_SDATA_IN_DRIVER))
-                iterator(data, sdata->vif.addr, &sdata->vif);
+        ASSERT_RTNL();
 
-        rcu_read_unlock();
+        __iterate_active_interfaces(local, iter_flags, iterator, data);
 }
-EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_atomic);
+EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_rtnl);
 
 /*
  * Nothing should have been stuffed into the workqueue during