From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antonio Quartulli Subject: [PATCH 1/8] batman-adv: Avoid recursive call_rcu for batadv_bla_claim Date: Sun, 17 Jan 2016 13:24:34 +0800 Message-ID: <1453008281-15396-2-git-send-email-a__16988.7753123932$1453008458$gmane$org@unstable.cc> References: <1453008281-15396-1-git-send-email-a@unstable.cc> Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org, Sven Eckelmann , Marek Lindner , Antonio Quartulli To: davem@davemloft.net Return-path: Received: from s1.neomailbox.net ([5.148.176.57]:8403 "EHLO s1.neomailbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750941AbcAQF0n (ORCPT ); Sun, 17 Jan 2016 00:26:43 -0500 In-Reply-To: <1453008281-15396-1-git-send-email-a@unstable.cc> Sender: netdev-owner@vger.kernel.org List-ID: From: Sven Eckelmann 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 Acked-by: Simon Wunderlich Signed-off-by: Marek Lindner Signed-off-by: Antonio Quartulli --- net/batman-adv/bridge_loop_avoidance.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c index d5d71ac96c8a..c24c481b666f 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); } /** -- 2.7.0