mac80211: fix mesh deadlock

The patch "cfg80211/mac80211: use cfg80211 wdev mutex in
mac80211" introduced several deadlocks by converting the
ifmsh->mtx to wdev->mtx. Solve these by:

1. drop the cancel_work_sync() in ieee80211_stop_mesh().
   Instead make the mesh work conditional on whether the mesh
   is running or not.
2. lock the mesh work with sdata_lock() to protect beacon
   updates and prevent races with wdev->mesh_id_len or
   cfg80211.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 18 insertions, 18 deletions

diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 73a597bad6e0..d5faf91632c1 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -579,9 +579,7 @@ static void ieee80211_mesh_housekeeping(struct ieee80211_sub_if_data *sdata)
         mesh_path_expire(sdata);
 
         changed = mesh_accept_plinks_update(sdata);
-        sdata_lock(sdata);
         ieee80211_mbss_info_change_notify(sdata, changed);
-        sdata_unlock(sdata);
 
         mod_timer(&ifmsh->housekeeping_timer,
                   round_jiffies(jiffies +
@@ -788,12 +786,10 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
         sdata->vif.bss_conf.enable_beacon = false;
         clear_bit(SDATA_STATE_OFFCHANNEL_BEACON_STOPPED, &sdata->state);
         ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON_ENABLED);
-        sdata_lock(sdata);
         bcn = rcu_dereference_protected(ifmsh->beacon,
                                         lockdep_is_held(&sdata->wdev.mtx));
         rcu_assign_pointer(ifmsh->beacon, NULL);
         kfree_rcu(bcn, rcu_head);
-        sdata_unlock(sdata);
 
         /* flush STAs and mpaths on this iface */
         sta_info_flush(sdata);
@@ -806,14 +802,6 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
         del_timer_sync(&sdata->u.mesh.housekeeping_timer);
         del_timer_sync(&sdata->u.mesh.mesh_path_root_timer);
         del_timer_sync(&sdata->u.mesh.mesh_path_timer);
-        /*
-         * If the timer fired while we waited for it, it will have
-         * requeued the work. Now the work will be running again
-         * but will not rearm the timer again because it checks
-         * whether the interface is running, which, at this point,
-         * it no longer is.
-         */
-        cancel_work_sync(&sdata->work);
 
         local->fif_other_bss--;
         atomic_dec(&local->iff_allmultis);
@@ -954,6 +942,12 @@ void ieee80211_mesh_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
         struct ieee80211_mgmt *mgmt;
         u16 stype;
 
+        sdata_lock(sdata);
+
+        /* mesh already went down */
+        if (!sdata->wdev.mesh_id_len)
+                goto out;
+
         rx_status = IEEE80211_SKB_RXCB(skb);
         mgmt = (struct ieee80211_mgmt *) skb->data;
         stype = le16_to_cpu(mgmt->frame_control) & IEEE80211_FCTL_STYPE;
@@ -971,12 +965,20 @@ void ieee80211_mesh_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
                 ieee80211_mesh_rx_mgmt_action(sdata, mgmt, skb->len, rx_status);
                 break;
         }
+out:
+        sdata_unlock(sdata);
 }
 
 void ieee80211_mesh_work(struct ieee80211_sub_if_data *sdata)
 {
         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 
+        sdata_lock(sdata);
+
+        /* mesh already went down */
+        if (!sdata->wdev.mesh_id_len)
+                goto out;
+
         if (ifmsh->preq_queue_len &&
             time_after(jiffies,
                        ifmsh->last_preq + msecs_to_jiffies(ifmsh->mshcfg.dot11MeshHWMPpreqMinInterval)))
@@ -996,6 +998,9 @@ void ieee80211_mesh_work(struct ieee80211_sub_if_data *sdata)
 
         if (test_and_clear_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags))
                 mesh_sync_adjust_tbtt(sdata);
+
+out:
+        sdata_unlock(sdata);
 }
 
 void ieee80211_mesh_notify_scan_completed(struct ieee80211_local *local)
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 6c4da99bc4fb..09bebed99416 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -517,9 +517,7 @@ void mesh_neighbour_update(struct ieee80211_sub_if_data *sdata,
         ieee80211_mps_frame_release(sta, elems);
 out:
         rcu_read_unlock();
-        sdata_lock(sdata);
         ieee80211_mbss_info_change_notify(sdata, changed);
-        sdata_unlock(sdata);
 }
 
 static void mesh_plink_timer(unsigned long data)
@@ -1070,9 +1068,6 @@ void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata,
 
         rcu_read_unlock();
 
-        if (changed) {
-                sdata_lock(sdata);
+        if (changed)
                 ieee80211_mbss_info_change_notify(sdata, changed);
-                sdata_unlock(sdata);
-        }
 }