From: Linus Lüssing linus.luessing@web.de

rcu_barrier() only waits for the currently scheduled rcu functions to finish - it won't wait for any function scheduled via another call_rcu() within an rcu scheduled function.

Unfortunately our batadv_tt_orig_list_entry_free_ref() does just that, via a batadv_orig_node_free_ref() call, leading to our rcu_barrier() call potentially missing such a batadv_orig_node_free_ref().

This patch fixes this issue by calling the batadv_orig_node_free_rcu() directly from the rcu callback, removing the unnecessary, additional call_rcu() layer here.

Signed-off-by: Linus Lüssing linus.luessing@web.de Signed-off-by: Marek Lindner lindner_marek@yahoo.de Acked-by: Antonio Quartulli ordex@autistici.org Signed-off-by: Antonio Quartulli ordex@autistici.org --- net/batman-adv/originator.c | 16 ++++++++++++++++ net/batman-adv/originator.h | 1 + net/batman-adv/translation-table.c | 7 ++++++- 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c index 2f34525..fad1a20 100644 --- a/net/batman-adv/originator.c +++ b/net/batman-adv/originator.c @@ -156,12 +156,28 @@ static void batadv_orig_node_free_rcu(struct rcu_head *rcu) kfree(orig_node); }

+/** + * batadv_orig_node_free_ref - decrement the orig node refcounter and possibly + * schedule an rcu callback for freeing it + * @orig_node: the orig node to free + */ void batadv_orig_node_free_ref(struct batadv_orig_node *orig_node) { if (atomic_dec_and_test(&orig_node->refcount)) call_rcu(&orig_node->rcu, batadv_orig_node_free_rcu); }

+/** + * batadv_orig_node_free_ref_now - decrement the orig node refcounter and + * possibly free it (without rcu callback) + * @orig_node: the orig node to free + */ +void batadv_orig_node_free_ref_now(struct batadv_orig_node *orig_node) +{ + if (atomic_dec_and_test(&orig_node->refcount)) + batadv_orig_node_free_rcu(&orig_node->rcu); +} + void batadv_originator_free(struct batadv_priv *bat_priv) { struct batadv_hashtable *hash = bat_priv->orig_hash; diff --git a/net/batman-adv/originator.h b/net/batman-adv/originator.h index 7df48fa..734e5a3 100644 --- a/net/batman-adv/originator.h +++ b/net/batman-adv/originator.h @@ -26,6 +26,7 @@ int batadv_originator_init(struct batadv_priv *bat_priv); void batadv_originator_free(struct batadv_priv *bat_priv); void batadv_purge_orig_ref(struct batadv_priv *bat_priv); void batadv_orig_node_free_ref(struct batadv_orig_node *orig_node); +void batadv_orig_node_free_ref_now(struct batadv_orig_node *orig_node); struct batadv_orig_node *batadv_get_orig_node(struct batadv_priv *bat_priv, const uint8_t *addr); struct batadv_neigh_node * diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index 5e89dee..9e87485 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -144,7 +144,12 @@ static void batadv_tt_orig_list_entry_free_rcu(struct rcu_head *rcu) struct batadv_tt_orig_list_entry *orig_entry;

orig_entry = container_of(rcu, struct batadv_tt_orig_list_entry, rcu); - batadv_orig_node_free_ref(orig_entry->orig_node); + + /* We are in an rcu callback here, therefore we cannot use + * batadv_orig_node_free_ref() and its call_rcu(): + * An rcu_barrier() wouldn't wait for that to finish + */ + batadv_orig_node_free_ref_now(orig_entry->orig_node); kfree(orig_entry); }