[B.A.T.M.A.N.] [PATCH v2 08/30] batman-adv: Drop immediate neigh_ifinfo free function

Sven Eckelmann
2015-12-20T13:17:48Z

It is not allowed to free the memory of an object which is part of a list
which is protected by rcu-read-side-critical sections without making sure
that no other context is accessing the object anymore. This usually happens
by removing the references to this object and then waiting until the rcu
grace period is over and no one (allowedly) accesses it anymore.

But the _now functions ignore this completely. They free the object
directly even when a different context still tries to access it. This has
to be avoided and thus these functions must be removed and all functions
have to use batadv_neigh_ifinfo_free_ref.

Fixes: 9bb33b8d88e3 ("batman-adv: split tq information in neigh_node struct")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
v2:
- split patchset into fixes and kref migration to make it easier when the
decision is made where each patch will be applied

net/batman-adv/originator.c | 32 +++++++++-----------------------
1 file changed, 9 insertions(+), 23 deletions(-)

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index 38da601..540aa2c 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -169,31 +169,17 @@ err:
}

/**
- * batadv_neigh_ifinfo_free_rcu - free the neigh_ifinfo object
- * @rcu: rcu pointer of the neigh_ifinfo object
- */
-static void batadv_neigh_ifinfo_free_rcu(struct rcu_head *rcu)
-{
- struct batadv_neigh_ifinfo *neigh_ifinfo;
-
- neigh_ifinfo = container_of(rcu, struct batadv_neigh_ifinfo, rcu);
-
- if (neigh_ifinfo->if_outgoing != BATADV_IF_DEFAULT)
- batadv_hardif_free_ref_now(neigh_ifinfo->if_outgoing);
-
- kfree(neigh_ifinfo);
-}
-
-/**
- * batadv_neigh_ifinfo_free_now - decrement the refcounter and possibly free
- * the neigh_ifinfo (without rcu callback)
+ * batadv_neigh_ifinfo_release - release neigh_ifinfo from lists and queue for
+ * free after rcu grace period
* @neigh_ifinfo: the neigh_ifinfo object to release
*/
static void
-batadv_neigh_ifinfo_free_ref_now(struct batadv_neigh_ifinfo *neigh_ifinfo)
+batadv_neigh_ifinfo_release(struct batadv_neigh_ifinfo *neigh_ifinfo)
{
- if (atomic_dec_and_test(&neigh_ifinfo->refcount))
- batadv_neigh_ifinfo_free_rcu(&neigh_ifinfo->rcu);
+ if (neigh_ifinfo->if_outgoing != BATADV_IF_DEFAULT)
+ batadv_hardif_free_ref(neigh_ifinfo->if_outgoing);
+
+ kfree_rcu(neigh_ifinfo, rcu);
}

/**
@@ -204,7 +190,7 @@ batadv_neigh_ifinfo_free_ref_now(struct batadv_neigh_ifinfo *neigh_ifinfo)
void batadv_neigh_ifinfo_free_ref(struct batadv_neigh_ifinfo *neigh_ifinfo)
{
if (atomic_dec_and_test(&neigh_ifinfo->refcount))
- call_rcu(&neigh_ifinfo->rcu, batadv_neigh_ifinfo_free_rcu);
+ batadv_neigh_ifinfo_release(neigh_ifinfo);
}

/**
@@ -251,7 +237,7 @@ static void batadv_neigh_node_free_rcu(struct rcu_head *rcu)

hlist_for_each_entry_safe(neigh_ifinfo, node_tmp,
&neigh_node->ifinfo_list, list) {
- batadv_neigh_ifinfo_free_ref_now(neigh_ifinfo);
+ batadv_neigh_ifinfo_free_ref(neigh_ifinfo);
}

hardif_neigh = batadv_hardif_neigh_get(neigh_node->if_incoming,
--
2.6.4