From 9c4604a298e0a9807eaf2cd912d1ebf24d98fbeb Mon Sep 17 00:00:00 2001 From: Sven Eckelmann Date: Sun, 26 Jun 2016 11:16:10 +0200 Subject: batman-adv: Fix use-after-free/double-free of tt_req_node The tt_req_node is added and removed from a list inside a spinlock. But the locking is sometimes removed even when the object is still referenced and will be used later via this reference. For example batadv_send_tt_request can create a new tt_req_node (including add to a list) and later re-acquires the lock to remove it from the list and to free it. But at this time another context could have already removed this tt_req_node from the list and freed it. CPU#0 batadv_batman_skb_recv from net_device 0 -> batadv_iv_ogm_receive -> batadv_iv_ogm_process -> batadv_iv_ogm_process_per_outif -> batadv_tvlv_ogm_receive -> batadv_tvlv_ogm_receive -> batadv_tvlv_containers_process -> batadv_tvlv_call_handler -> batadv_tt_tvlv_ogm_handler_v1 -> batadv_tt_update_orig -> batadv_send_tt_request -> batadv_tt_req_node_new spin_lock(...) allocates new tt_req_node and adds it to list spin_unlock(...) return tt_req_node CPU#1 batadv_batman_skb_recv from net_device 1 -> batadv_recv_unicast_tvlv -> batadv_tvlv_containers_process -> batadv_tvlv_call_handler -> batadv_tt_tvlv_unicast_handler_v1 -> batadv_handle_tt_response spin_lock(...) tt_req_node gets removed from list and is freed spin_unlock(...) CPU#0 <- returned to batadv_send_tt_request spin_lock(...) tt_req_node gets removed from list and is freed MEMORY CORRUPTION/SEGFAULT/... spin_unlock(...) This can only be solved via reference counting to allow multiple contexts to handle the list manipulation while making sure that only the last context holding a reference will free the object. Fixes: a73105b8d4c7 ("batman-adv: improved client announcement mechanism") Signed-off-by: Sven Eckelmann Tested-by: Martin Weinelt Tested-by: Amadeus Alfa Signed-off-by: Marek Lindner Signed-off-by: David S. Miller --- net/batman-adv/types.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/batman-adv/types.h') diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index 6a577f4f8ba7..ba846b078af8 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -1137,11 +1137,13 @@ struct batadv_tt_change_node { * struct batadv_tt_req_node - data to keep track of the tt requests in flight * @addr: mac address address of the originator this request was sent to * @issued_at: timestamp used for purging stale tt requests + * @refcount: number of contexts the object is used by * @list: list node for batadv_priv_tt::req_list */ struct batadv_tt_req_node { u8 addr[ETH_ALEN]; unsigned long issued_at; + struct kref refcount; struct hlist_node list; }; -- cgit v1.2.3