linux-kernel - [PATCH 3.16.y-ckt 170/180] batman-adv: Drop immediate batadv_hard

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Date:	Wed,  3 Feb 2016 22:32:56 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Sven Eckelmann <sven@...fation.org>,
	Marek Lindner <mareklindner@...mailbox.ch>,
	Antonio Quartulli <a@...table.cc>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 170/180] batman-adv: Drop immediate batadv_hard_iface free function

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Sven Eckelmann <sven@...fation.org>

commit b4d922cfc9c08318eeb77d53b7633740e6b0efb0 upstream.

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_hardif_free_ref.

Fixes: 89652331c00f ("batman-adv: split tq information in neigh_node struct")
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Antonio Quartulli <a@...table.cc>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 net/batman-adv/hard-interface.h | 12 ------------
 net/batman-adv/originator.c     | 15 +++++++--------
 2 files changed, 7 insertions(+), 20 deletions(-)

diff --git a/net/batman-adv/hard-interface.h b/net/batman-adv/hard-interface.h
index 1918cd50b62e..b6bff9c1877a 100644
--- a/net/batman-adv/hard-interface.h
+++ b/net/batman-adv/hard-interface.h
@@ -64,18 +64,6 @@ batadv_hardif_free_ref(struct batadv_hard_iface *hard_iface)
 		call_rcu(&hard_iface->rcu, batadv_hardif_free_rcu);
 }
 
-/**
- * batadv_hardif_free_ref_now - decrement the hard interface refcounter and
- *  possibly free it (without rcu callback)
- * @hard_iface: the hard interface to free
- */
-static inline void
-batadv_hardif_free_ref_now(struct batadv_hard_iface *hard_iface)
-{
-	if (atomic_dec_and_test(&hard_iface->refcount))
-		batadv_hardif_free_rcu(&hard_iface->rcu);
-}
-
 static inline struct batadv_hard_iface *
 batadv_primary_if_get_selected(struct batadv_priv *bat_priv)
 {
diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index 550f2561f9bf..2dd50cc29079 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -175,24 +175,23 @@ void batadv_neigh_ifinfo_free_ref(struct batadv_neigh_ifinfo *neigh_ifinfo)
 }
 
 /**
- * batadv_neigh_node_free_rcu - free the neigh_node
- * @rcu: rcu pointer of the neigh_node
+ * batadv_neigh_node_release - release neigh_node from lists and queue for
+ *  free after rcu grace period
+ * @neigh_node: neigh neighbor to free
  */
-static void batadv_neigh_node_free_rcu(struct rcu_head *rcu)
+static void batadv_neigh_node_release(struct batadv_neigh_node *neigh_node)
 {
 	struct hlist_node *node_tmp;
-	struct batadv_neigh_node *neigh_node;
 	struct batadv_neigh_ifinfo *neigh_ifinfo;
 
-	neigh_node = container_of(rcu, struct batadv_neigh_node, rcu);
 
 	hlist_for_each_entry_safe(neigh_ifinfo, node_tmp,
 				  &neigh_node->ifinfo_list, list) {
 		batadv_neigh_ifinfo_free_ref(neigh_ifinfo);
 	}
-	batadv_hardif_free_ref_now(neigh_node->if_incoming);
+	batadv_hardif_free_ref(neigh_node->if_incoming);
 
-	kfree(neigh_node);
+	kfree_rcu(neigh_node, rcu);
 }
 
 /**
@@ -203,7 +202,7 @@ static void batadv_neigh_node_free_rcu(struct rcu_head *rcu)
 void batadv_neigh_node_free_ref(struct batadv_neigh_node *neigh_node)
 {
 	if (atomic_dec_and_test(&neigh_node->refcount))
-		call_rcu(&neigh_node->rcu, batadv_neigh_node_free_rcu);
+		batadv_neigh_node_release(neigh_node);
 }
 
 /**