batman-adv: mcast: fix multicast tt/tvlv worker locking

commit a3c7cd0cdf1107f891aff847ad481e34df727055 upstream.

Syzbot has reported some issues with the locking assumptions made for
the multicast tt/tvlv worker: It was able to trigger the WARN_ON() in
batadv_mcast_mla_tt_retract() and batadv_mcast_mla_tt_add().
While hard/not reproduceable for us so far it seems that the
delayed_work_pending() we use might not be quite safe from reordering.

Therefore this patch adds an explicit, new spinlock to protect the
update of the mla_list and flags in bat_priv and then removes the
WARN_ON(delayed_work_pending()).

Reported-by: syzbot+83f2d54ec6b7e417e13f@syzkaller.appspotmail.com
Reported-by: syzbot+050927a651272b145a5d@syzkaller.appspotmail.com
Reported-by: syzbot+979ffc89b87309b1b94b@syzkaller.appspotmail.com
Reported-by: syzbot+f9f3f388440283da2965@syzkaller.appspotmail.com
Fixes: cbebd363b2e9 ("batman-adv: Use own timer for multicast TT and TVLV updates")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index 69c0d85..79b8a2d 100644 (file)
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -160,6 +160,7 @@ int batadv_mesh_init(struct net_device *soft_iface)
        spin_lock_init(&bat_priv->tt.commit_lock);
        spin_lock_init(&bat_priv->gw.list_lock);
 #ifdef CONFIG_BATMAN_ADV_MCAST
+       spin_lock_init(&bat_priv->mcast.mla_lock);
        spin_lock_init(&bat_priv->mcast.want_lists_lock);
 #endif
        spin_lock_init(&bat_priv->tvlv.container_list_lock);

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 86725d7..b90fe25 100644 (file)
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -325,8 +325,6 @@ static void batadv_mcast_mla_list_free(struct hlist_head *mcast_list)
  * translation table except the ones listed in the given mcast_list.
  *
  * If mcast_list is NULL then all are retracted.
- *
- * Do not call outside of the mcast worker! (or cancel mcast worker first)
  */
 static void batadv_mcast_mla_tt_retract(struct batadv_priv *bat_priv,
                                        struct hlist_head *mcast_list)
@@ -334,8 +332,6 @@ static void batadv_mcast_mla_tt_retract(struct batadv_priv *bat_priv,
        struct batadv_hw_addr *mcast_entry;
        struct hlist_node *tmp;
 
-       WARN_ON(delayed_work_pending(&bat_priv->mcast.work));
-
        hlist_for_each_entry_safe(mcast_entry, tmp, &bat_priv->mcast.mla_list,
                                  list) {
                if (mcast_list &&
@@ -359,8 +355,6 @@ static void batadv_mcast_mla_tt_retract(struct batadv_priv *bat_priv,
  *
  * Adds multicast listener announcements from the given mcast_list to the
  * translation table if they have not been added yet.
- *
- * Do not call outside of the mcast worker! (or cancel mcast worker first)
  */
 static void batadv_mcast_mla_tt_add(struct batadv_priv *bat_priv,
                                    struct hlist_head *mcast_list)
@@ -368,8 +362,6 @@ static void batadv_mcast_mla_tt_add(struct batadv_priv *bat_priv,
        struct batadv_hw_addr *mcast_entry;
        struct hlist_node *tmp;
 
-       WARN_ON(delayed_work_pending(&bat_priv->mcast.work));
-
        if (!mcast_list)
                return;
 
@@ -658,7 +650,10 @@ static void batadv_mcast_mla_update(struct work_struct *work)
        priv_mcast = container_of(delayed_work, struct batadv_priv_mcast, work);
        bat_priv = container_of(priv_mcast, struct batadv_priv, mcast);
 
+       spin_lock(&bat_priv->mcast.mla_lock);
        __batadv_mcast_mla_update(bat_priv);
+       spin_unlock(&bat_priv->mcast.mla_lock);
+
        batadv_mcast_start_timer(bat_priv);
 }
 

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 343d304..eeee3e6 100644 (file)
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -1216,6 +1216,11 @@ struct batadv_priv_mcast {
        unsigned char bridged:1;
 
        /**
+        * @mla_lock: a lock protecting mla_list and mla_flags
+        */
+       spinlock_t mla_lock;
+
+       /**
         * @num_want_all_unsnoopables: number of nodes wanting unsnoopable IP
         *  traffic
         */