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routing/batman-adv/patches/0014-batman-adv-Fix-use-after-free-double-free-of-tt_req_.patch
Sven Eckelmann f1f7684c2c batman-adv: Add fixes from upcoming 2016.2 release 
The upcoming batman-adv 2016.2 contains multiple new features, code
refactoring and similar things. These may not be fitting for Chaos Calmer
but the changes in the maintenance branch (bugfixes) should be integrated
to increase the stability.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
2016-06-07 08:14:51 +02:00

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From: Sven Eckelmann <sven@narfation.org>
Date: Sat, 4 Jun 2016 08:52:12 +0200
Subject: [PATCH] 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: cea194d90b11 ("batman-adv: improved client announcement mechanism")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Tested-by: Martin Weinelt <martin@darmstadt.freifunk.net>
Tested-by: Amadeus Alfa <amadeus@chemnitz.freifunk.net>
Origin: upstream, https://git.open-mesh.org/batman-adv.git/commit/c3fef3d9ec6e8b882f321ec20f6f2cb2ee906503
---
net/batman-adv/translation-table.c | 37 +++++++++++++++++++++++++++++++++----
net/batman-adv/types.h | 2 ++
2 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 5ed782b..23fb7ea 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -2271,6 +2271,29 @@ static u32 batadv_tt_local_crc(struct batadv_priv *bat_priv,
return crc;
}
+/**
+ * batadv_tt_req_node_release - free tt_req node entry
+ * @ref: kref pointer of the tt req_node entry
+ */
+static void batadv_tt_req_node_release(struct kref *ref)
+{
+ struct batadv_tt_req_node *tt_req_node;
+
+ tt_req_node = container_of(ref, struct batadv_tt_req_node, refcount);
+
+ kfree(tt_req_node);
+}
+
+/**
+ * batadv_tt_req_node_put - decrement the tt_req_node refcounter and
+ * possibly release it
+ * @tt_req_node: tt_req_node to be free'd
+ */
+static void batadv_tt_req_node_put(struct batadv_tt_req_node *tt_req_node)
+{
+ kref_put(&tt_req_node->refcount, batadv_tt_req_node_release);
+}
+
static void batadv_tt_req_list_free(struct batadv_priv *bat_priv)
{
struct batadv_tt_req_node *node;
@@ -2280,7 +2303,7 @@ static void batadv_tt_req_list_free(struct batadv_priv *bat_priv)
hlist_for_each_entry_safe(node, safe, &bat_priv->tt.req_list, list) {
hlist_del_init(&node->list);
- kfree(node);
+ batadv_tt_req_node_put(node);
}
spin_unlock_bh(&bat_priv->tt.req_list_lock);
@@ -2317,7 +2340,7 @@ static void batadv_tt_req_purge(struct batadv_priv *bat_priv)
if (batadv_has_timed_out(node->issued_at,
BATADV_TT_REQUEST_TIMEOUT)) {
hlist_del_init(&node->list);
- kfree(node);
+ batadv_tt_req_node_put(node);
}
}
spin_unlock_bh(&bat_priv->tt.req_list_lock);
@@ -2349,9 +2372,11 @@ batadv_tt_req_node_new(struct batadv_priv *bat_priv,
if (!tt_req_node)
goto unlock;
+ kref_init(&tt_req_node->refcount);
ether_addr_copy(tt_req_node->addr, orig_node->orig);
tt_req_node->issued_at = jiffies;
+ kref_get(&tt_req_node->refcount);
hlist_add_head(&tt_req_node->list, &bat_priv->tt.req_list);
unlock:
spin_unlock_bh(&bat_priv->tt.req_list_lock);
@@ -2618,9 +2643,13 @@ out:
spin_lock_bh(&bat_priv->tt.req_list_lock);
/* hlist_del_init() verifies tt_req_node still is in the list */
hlist_del_init(&tt_req_node->list);
+ batadv_tt_req_node_put(tt_req_node);
spin_unlock_bh(&bat_priv->tt.req_list_lock);
- kfree(tt_req_node);
}
+
+ if (tt_req_node)
+ batadv_tt_req_node_put(tt_req_node);
+
kfree(tvlv_tt_data);
return ret;
}
@@ -3056,7 +3085,7 @@ static void batadv_handle_tt_response(struct batadv_priv *bat_priv,
if (!batadv_compare_eth(node->addr, resp_src))
continue;
hlist_del_init(&node->list);
- kfree(node);
+ batadv_tt_req_node_put(node);
}
spin_unlock_bh(&bat_priv->tt.req_list_lock);
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 1e47fbe..d75beef 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -1129,11 +1129,13 @@ 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;
};
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