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batman-adv: Prevent duplicated tvlv handler

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The function batadv_tvlv_handler_register is responsible for adding new
tvlv_handler to the handler_list. It first checks whether the entry
already is in the list or not. If it is, then the creation of a new entry
is aborted.

But the lock for the list is only held when the list is really modified.
This could lead to duplicated entries because another context could create
an entry with the same key between the check and the list manipulation.

The check and the manipulation of the list must therefore be in the same
locked code section.

Fixes: ef26157747d4 ("batman-adv: tvlv - basic infrastructure")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
This commit is contained in:
Sven Eckelmann 2018-08-12 21:04:45 +02:00 committed by Simon Wunderlich
parent e7136e48ff
commit ae3cdc97dc
1 changed files with 6 additions and 2 deletions
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8
net/batman-adv/tvlv.c
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@ -529,15 +529,20 @@ void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
{
struct batadv_tvlv_handler *tvlv_handler;
spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
tvlv_handler = batadv_tvlv_handler_get(bat_priv, type, version);
if (tvlv_handler) {
spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
batadv_tvlv_handler_put(tvlv_handler);
return;
}
tvlv_handler = kzalloc(sizeof(*tvlv_handler), GFP_ATOMIC);
if (!tvlv_handler)
if (!tvlv_handler) {
spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
return;
}
tvlv_handler->ogm_handler = optr;
tvlv_handler->unicast_handler = uptr;
@ -547,7 +552,6 @@ void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
kref_init(&tvlv_handler->refcount);
INIT_HLIST_NODE(&tvlv_handler->list);
spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
kref_get(&tvlv_handler->refcount);
hlist_add_head_rcu(&tvlv_handler->list, &bat_priv->tvlv.handler_list);
spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);