From: Sven Eckelmann sven@narfation.org

The router is put down twice when it was non-NULL and either orig_ifinfo is NULL afterwards or batman-adv receives a packet with the same sequence number. This will end up in a use-after-free when the batadv_neigh_node is removed because the reference counter ended up too early at 0.

Fixes: 9323158ef9f4 ("batman-adv: OGMv2 - implement originators logic") Signed-off-by: Sven Eckelmann sven@narfation.org Signed-off-by: Antonio Quartulli a@unstable.cc ---

This patch is skipping netdev and is being sent directly to stable in accordance with David S. Miller[1].

The reason is that this patch applies only on linux-4.6 and not on linux-4.7/net because it was "accidentally" fixed by a refactoring commit (more details in [2]).

It addresses a reference imbalance which systematically leads to a use-after-free and then a kernel crash.

Cheers,

[1] https://www.mail-archive.com/b.a.t.m.a.n@lists.open-mesh.org/msg15258.html [2] https://www.mail-archive.com/b.a.t.m.a.n@lists.open-mesh.org/msg15252.html

net/batman-adv/bat_v_ogm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/bat_v_ogm.c b/net/batman-adv/bat_v_ogm.c index d9bcbe6e7d65..91df28a100f9 100644 --- a/net/batman-adv/bat_v_ogm.c +++ b/net/batman-adv/bat_v_ogm.c @@ -529,8 +529,10 @@ static void batadv_v_ogm_route_update(struct batadv_priv *bat_priv, goto out; }

- if (router) + if (router) { batadv_neigh_node_put(router); + router = NULL; + }

/* Update routes, and check if the OGM is from the best next hop */ batadv_v_ogm_orig_update(bat_priv, orig_node, neigh_node, ogm2,