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>

diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 73a597bad6e021a806a6f9ee491f70fce231946e..d5faf91632c12d494b06ac66fcf4a606bfb3b549 100644 (file)
--- 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 6c4da99bc4fb392f610bf57b76865f1940cccb60..09bebed99416d1f848dd95f98cf488de20a36fdf 100644 (file)
--- 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);
-       }
 }