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batman-adv: Add missing refcnt for last_candidate

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commit 936523441bb64cdc9a5b263e8fd2782e70313a57 upstream.

batadv_find_router dereferences last_bonding_candidate from
orig_node without making sure that it has a valid reference. This reference
has to be retrieved by increasing the reference counter while holding
neigh_list_lock. The lock is required to avoid that
batadv_last_bonding_replace removes the current last_bonding_candidate,
reduces the reference counter and maybe destroys the object in this
process.

Fixes: f3b3d9018975 ("batman-adv: add bonding again")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sven Eckelmann 2020-03-18 00:27:10 +01:00 committed by Greg Kroah-Hartman
parent bfab05e446
commit 1428d49024
1 changed files with 27 additions and 1 deletions
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28
net/batman-adv/routing.c
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@ -439,6 +439,29 @@ static int batadv_check_unicast_packet(struct batadv_priv *bat_priv,
return 0;
}
/**
* batadv_last_bonding_get - Get last_bonding_candidate of orig_node
* @orig_node: originator node whose last bonding candidate should be retrieved
*
* Return: last bonding candidate of router or NULL if not found
*
* The object is returned with refcounter increased by 1.
*/
static struct batadv_orig_ifinfo *
batadv_last_bonding_get(struct batadv_orig_node *orig_node)
{
struct batadv_orig_ifinfo *last_bonding_candidate;
spin_lock_bh(&orig_node->neigh_list_lock);
last_bonding_candidate = orig_node->last_bonding_candidate;
if (last_bonding_candidate)
atomic_inc(&last_bonding_candidate->refcount);
spin_unlock_bh(&orig_node->neigh_list_lock);
return last_bonding_candidate;
}
/**
* batadv_last_bonding_replace - Replace last_bonding_candidate of orig_node
* @orig_node: originator node whose bonding candidates should be replaced
@ -509,7 +532,7 @@ batadv_find_router(struct batadv_priv *bat_priv,
* router - obviously there are no other candidates.
*/
rcu_read_lock();
last_candidate = orig_node->last_bonding_candidate;
last_candidate = batadv_last_bonding_get(orig_node);
if (last_candidate)
last_cand_router = rcu_dereference(last_candidate->router);
@ -601,6 +624,9 @@ next:
batadv_orig_ifinfo_free_ref(next_candidate);
}
if (last_candidate)
batadv_orig_ifinfo_free_ref(last_candidate);
return router;
}