On Friday, 18 September 2020 05:03:19 CEST Xiyu Yang wrote:
batadv_neigh_node_create() is used to create a neigh node object, whose fields will be initialized with the specific object. When a new reference of the specific object is created during the initialization, its refcount should be increased.
However, when "neigh_node" object initializes its orig_node field with the "orig_node" object, the function forgets to hold the refcount of the "orig_node", causing a potential refcount leak and use-after-free issue for the reason that the object can be freed in other places.
Fix this issue by increasing the refcount of orig_node object during the initialization and adding corresponding batadv_orig_node_put() in batadv_neigh_node_release().
I will most likely not add this patch because I have concerns that this would need an active garbage collector to fix the reference counter loop.
Please check batadv_neigh_node::orig_node (whose reference counter you've just incremented) and batadv_orig_node::neigh_list (with batadv_neigh_node). And at the same time the batadv_neigh_node_release and batadv_orig_node_release. So the originator will only free the reference (and thus potentially call batadv_neigh_node_release) when its own reference counter is zero. But it cannot become zero because the neigh_node is holding a reference to this originator.
Kind regards, Sven