batman-adv: Correct rcu refcounting for orig_node
It might be possible that 2 threads access the same data in the same
rcu grace period. The first thread calls call_rcu() to decrement the
refcount and free the data while the second thread increases the
refcount to use the data. To avoid this race condition all refcount
operations have to be atomic.
Reported-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 41eba8a..3cc4355 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -53,9 +53,11 @@
goto out;
orig_node = curr_gateway_tmp->orig_node;
+ if (!orig_node)
+ goto out;
- if (orig_node)
- kref_get(&orig_node->refcount);
+ if (!atomic_inc_not_zero(&orig_node->refcount))
+ orig_node = NULL;
out:
rcu_read_unlock();