diff options
author | Sven Eckelmann <sven@narfation.org> | 2016-06-26 09:16:10 (GMT) |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-06-29 08:01:47 (GMT) |
commit | 9c4604a298e0a9807eaf2cd912d1ebf24d98fbeb (patch) | |
tree | d05371bad42efcf81f85aff5ce08b048b943b119 /net/batman-adv | |
parent | 0b3dd7dfb81ad8af53791ea2bb64b83bac1b7d32 (diff) | |
download | linux-9c4604a298e0a9807eaf2cd912d1ebf24d98fbeb.tar.xz |
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 <sven@narfation.org>
Tested-by: Martin Weinelt <martin@darmstadt.freifunk.net>
Tested-by: Amadeus Alfa <amadeus@chemnitz.freifunk.net>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/batman-adv')
-rw-r--r-- | net/batman-adv/translation-table.c | 43 | ||||
-rw-r--r-- | net/batman-adv/types.h | 2 |
2 files changed, 39 insertions, 6 deletions
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index 72abab7..cfb5ccd 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); @@ -2615,13 +2640,19 @@ static bool batadv_send_tt_request(struct batadv_priv *bat_priv, out: if (primary_if) batadv_hardif_put(primary_if); + if (ret && tt_req_node) { 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); + if (!hlist_unhashed(&tt_req_node->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; } @@ -3057,7 +3088,7 @@ 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 6a577f4..ba846b0 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; }; |