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Commit 72822225 authored by Linus Lüssing's avatar Linus Lüssing Committed by Antonio Quartulli
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batman-adv: Fix rcu_barrier() miss due to double call_rcu() in TT code 



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: default avatarLinus Lüssing <linus.luessing@web.de>
Signed-off-by: default avatarMarek Lindner <lindner_marek@yahoo.de>
Acked-by: default avatarAntonio Quartulli <ordex@autistici.org>
parent b0ce3508

net/batman-adv/originator.c

+16 −0
Original line number Diff line number Diff line
@@ -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;

net/batman-adv/originator.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *

net/batman-adv/translation-table.c

+6 −1
Original line number Diff line number Diff line
@@ -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);

}