[linux-next] LinuxNextTracking branch, master, updated. next-20160118

batman at open-mesh.org batman at open-mesh.org
Tue Jan 19 00:15:45 CET 2016


The following commit has been merged in the master branch:
commit 63b399272294e7a939cde41792dca38c549f0484
Author: Sven Eckelmann <sven at narfation.org>
Date:   Thu Jan 14 15:28:19 2016 +0100

    batman-adv: Avoid recursive call_rcu for batadv_bla_claim
    
    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: 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
    Signed-off-by: Sven Eckelmann <sven at narfation.org>
    Acked-by: Simon Wunderlich <sw at simonwunderlich.de>
    Signed-off-by: Marek Lindner <mareklindner at neomailbox.ch>
    Signed-off-by: Antonio Quartulli <a at unstable.cc>

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index d5d71ac..c24c481 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -127,21 +127,17 @@ batadv_backbone_gw_free_ref(struct batadv_bla_backbone_gw *backbone_gw)
 }
 
 /* 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);
-	kfree(claim);
+	kfree_rcu(claim, rcu);
 }
 
 /* free a claim, call claim_free_rcu if its the last reference */
 static void batadv_claim_free_ref(struct batadv_bla_claim *claim)
 {
 	if (atomic_dec_and_test(&claim->refcount))
-		call_rcu(&claim->rcu, batadv_claim_free_rcu);
+		batadv_claim_release(claim);
 }
 
 /**

-- 
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