Commit 3816a728 authored by Sven Eckelmann's avatar Sven Eckelmann Committed by Luis Henriques

batman-adv: Avoid recursive call_rcu for batadv_bla_claim

commit 63b39927 upstream.

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>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 9647516f
...@@ -113,21 +113,17 @@ batadv_backbone_gw_free_ref(struct batadv_bla_backbone_gw *backbone_gw) ...@@ -113,21 +113,17 @@ batadv_backbone_gw_free_ref(struct batadv_bla_backbone_gw *backbone_gw)
} }
/* finally deinitialize the claim */ /* finally deinitialize the claim */
static void batadv_claim_free_rcu(struct rcu_head *rcu) static void batadv_claim_release(struct batadv_bla_claim *claim)
{ {
struct batadv_bla_claim *claim;
claim = container_of(rcu, struct batadv_bla_claim, rcu);
batadv_backbone_gw_free_ref(claim->backbone_gw); batadv_backbone_gw_free_ref(claim->backbone_gw);
kfree(claim); kfree_rcu(claim, rcu);
} }
/* free a claim, call claim_free_rcu if its the last reference */ /* free a claim, call claim_free_rcu if its the last reference */
static void batadv_claim_free_ref(struct batadv_bla_claim *claim) static void batadv_claim_free_ref(struct batadv_bla_claim *claim)
{ {
if (atomic_dec_and_test(&claim->refcount)) if (atomic_dec_and_test(&claim->refcount))
call_rcu(&claim->rcu, batadv_claim_free_rcu); batadv_claim_release(claim);
} }
/** /**
......
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