The neigh_list with batadv_hardif_neigh_node objects is accessed with only rcu_read_lock in batadv_neigh_node_get and batadv_iv_neigh_print. Thus is is not allowed to kfree the object before the rcu grace period ends which may still tries to access this object. Therefore the object has first to be removed from the neigh_list and then it has either wait with synchronize_rcu or call_rcu till the grace period ends before it can be freed.
Signed-off-by: Sven Eckelmann sven@narfation.org --- I have no idea why batadv_hardif_neigh_free_now is considered to be safe to call. The only caller is batadv_neigh_node_free_rcu but this function never makes sure that the previously mentioned two functions are actually not accessing it right now when hlist_del_rcu_init + kfree is called. --- net/batman-adv/originator.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c index 00b0437..2681c7d 100644 --- a/net/batman-adv/originator.c +++ b/net/batman-adv/originator.c @@ -217,10 +217,6 @@ static void batadv_hardif_neigh_free_rcu(struct rcu_head *rcu)
hardif_neigh = container_of(rcu, struct batadv_hardif_neigh_node, rcu);
- spin_lock_bh(&hardif_neigh->if_incoming->neigh_list_lock); - hlist_del_init_rcu(&hardif_neigh->list); - spin_unlock_bh(&hardif_neigh->if_incoming->neigh_list_lock); - batadv_hardif_free_ref_now(hardif_neigh->if_incoming); kfree(hardif_neigh); } @@ -233,8 +229,13 @@ static void batadv_hardif_neigh_free_rcu(struct rcu_head *rcu) static void batadv_hardif_neigh_free_now(struct batadv_hardif_neigh_node *hardif_neigh) { - if (atomic_dec_and_test(&hardif_neigh->refcount)) + if (atomic_dec_and_test(&hardif_neigh->refcount)) { + spin_lock_bh(&hardif_neigh->if_incoming->neigh_list_lock); + hlist_del_init_rcu(&hardif_neigh->list); + spin_unlock_bh(&hardif_neigh->if_incoming->neigh_list_lock); + batadv_hardif_neigh_free_rcu(&hardif_neigh->rcu); + } }
/** @@ -244,8 +245,13 @@ batadv_hardif_neigh_free_now(struct batadv_hardif_neigh_node *hardif_neigh) */ void batadv_hardif_neigh_free_ref(struct batadv_hardif_neigh_node *hardif_neigh) { - if (atomic_dec_and_test(&hardif_neigh->refcount)) + if (atomic_dec_and_test(&hardif_neigh->refcount)) { + spin_lock_bh(&hardif_neigh->if_incoming->neigh_list_lock); + hlist_del_init_rcu(&hardif_neigh->list); + spin_unlock_bh(&hardif_neigh->if_incoming->neigh_list_lock); + call_rcu(&hardif_neigh->rcu, batadv_hardif_neigh_free_rcu); + } }
/**