batman-adv: Use kref_get for batadv_nc_get_nc_node

commit 0de32ceee156787429035c974316f4e5098cf722 upstream.

batadv_nc_get_nc_node requires that the caller already has a valid
reference for orig_neigh_node. It is therefore not possible that it has an
reference counter of 0 and was still given to this function

The kref_get function instead WARNs (with debug information) when the
reference counter would still be 0. This makes a bug in batman-adv better
visible because kref_get_unless_zero would have ignored this problem.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
[bwh: Backported to 3.16: Reference counts are not krefs here, so open-
 code the equivalent of kref_get()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index 4e718162a26b5eb17abaade82711525bd9f19a76..33ce5723a1a4f84bc7dcc097f3782d740614593d 100644 (file)
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -813,8 +813,7 @@ static struct batadv_nc_node
        if (!nc_node)
                return NULL;
 
-       if (!atomic_inc_not_zero(&orig_neigh_node->refcount))
-               goto free;
+       WARN_ON_ONCE(atomic_inc_return(&orig_neigh_node->refcount) < 2);
 
        /* Initialize nc_node */
        INIT_LIST_HEAD(&nc_node->list);
@@ -840,10 +839,6 @@ static struct batadv_nc_node
        spin_unlock_bh(lock);
 
        return nc_node;
-
-free:
-       kfree(nc_node);
-       return NULL;
 }
 
 /**