• Sven Eckelmann's avatar
    batman-adv: Avoid recursive call_rcu for batadv_bla_claim · 63b39927
    Sven Eckelmann authored
    The batadv_claim_free_ref function uses call_rcu to delay the free of the
    batadv_bla_claim object until no (already started) rcu_read_lock is enabled
    anymore. This makes sure that no context is still trying to access the
    object which should be removed. But batadv_bla_claim also contains a
    reference to backbone_gw which must be removed.
    
    The reference drop of backbone_gw was done in the call_rcu function
    batadv_claim_free_rcu but should actually be done in the
    batadv_claim_release function to avoid nested call_rcus. This is important
    because rcu_barrier (e.g. batadv_softif_free or batadv_exit) will not
    detect the inner call_rcu as relevant for its execution. Otherwise this
    barrier will most likely be inserted in the queue before the callback of
    the first call_rcu was executed. The caller of rcu_barrier will therefore
    continue to run before the inner call_rcu callback finished.
    
    Fixes: 23721387 ("batman-adv: add basic bridge loop avoidance code")
    Signed-off-by: default avatarSven Eckelmann <sven@narfation.org>
    Acked-by: default avatarSimon Wunderlich <sw@simonwunderlich.de>
    Signed-off-by: default avatarMarek Lindner <mareklindner@neomailbox.ch>
    Signed-off-by: default avatarAntonio Quartulli <a@unstable.cc>
    63b39927
bridge_loop_avoidance.c 49.1 KB