[maint] batman-adv: Add missing refcnt for last_candidate
Commit Message
batadv_find_router dereferences last_bonding_candidate from
orig_node without making sure that it has a valid reference. This reference
has to be retrieved by increasing the reference counter while holding
neigh_list_lock. The lock is required to avoid that
batadv_last_bonding_replace removes the current last_bonding_candidate,
reduces the reference counter and maybe destroys the object in this
process.
Fixes: 797edd9e87ac ("batman-adv: add bonding again")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
This patch was only build tested.
---
net/batman-adv/routing.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
Comments
On Saturday, August 6, 2016 3:50:52 PM HKT Sven Eckelmann wrote:
> batadv_find_router dereferences last_bonding_candidate from
> orig_node without making sure that it has a valid reference. This reference
> has to be retrieved by increasing the reference counter while holding
> neigh_list_lock. The lock is required to avoid that
> batadv_last_bonding_replace removes the current last_bonding_candidate,
> reduces the reference counter and maybe destroys the object in this
> process.
>
> Fixes: 797edd9e87ac ("batman-adv: add bonding again")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
> This patch was only build tested.
> ---
> net/batman-adv/routing.c | 28 +++++++++++++++++++++++++++-
> 1 file changed, 27 insertions(+), 1 deletion(-)
Applied in revision 008afae.
Thanks,
Marek
@@ -456,6 +456,29 @@ static int batadv_check_unicast_packet(struct batadv_priv *bat_priv,
}
/**
+ * batadv_last_bonding_get - Get last_bonding_candidate of orig_node
+ * @orig_node: originator node whose last bonding candidate should be retrieved
+ *
+ * Return: last bonding candidate of router or NULL if not found
+ *
+ * The object is returned with refcounter increased by 1.
+ */
+static struct batadv_orig_ifinfo *
+batadv_last_bonding_get(struct batadv_orig_node *orig_node)
+{
+ struct batadv_orig_ifinfo *last_bonding_candidate;
+
+ spin_lock_bh(&orig_node->neigh_list_lock);
+ last_bonding_candidate = orig_node->last_bonding_candidate;
+
+ if (last_bonding_candidate)
+ kref_get(&last_bonding_candidate->refcount);
+ spin_unlock_bh(&orig_node->neigh_list_lock);
+
+ return last_bonding_candidate;
+}
+
+/**
* batadv_last_bonding_replace - Replace last_bonding_candidate of orig_node
* @orig_node: originator node whose bonding candidates should be replaced
* @new_candidate: new bonding candidate or NULL
@@ -525,7 +548,7 @@ batadv_find_router(struct batadv_priv *bat_priv,
* router - obviously there are no other candidates.
*/
rcu_read_lock();
- last_candidate = orig_node->last_bonding_candidate;
+ last_candidate = batadv_last_bonding_get(orig_node);
if (last_candidate)
last_cand_router = rcu_dereference(last_candidate->router);
@@ -617,6 +640,9 @@ next:
batadv_orig_ifinfo_put(next_candidate);
}
+ if (last_candidate)
+ batadv_orig_ifinfo_put(last_candidate);
+
return router;
}