From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50994 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935089AbcA0SY0 (ORCPT ); Wed, 27 Jan 2016 13:24:26 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sven Eckelmann , Simon Wunderlich , Marek Lindner , Antonio Quartulli Subject: [PATCH 4.3 113/157] batman-adv: Avoid recursive call_rcu for batadv_bla_claim Date: Wed, 27 Jan 2016 10:13:00 -0800 Message-Id: <20160127180938.688957506@linuxfoundation.org> In-Reply-To: <20160127180932.533735338@linuxfoundation.org> References: <20160127180932.533735338@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: stable-owner@vger.kernel.org List-ID: 4.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sven Eckelmann [ Upstream commit 63b399272294e7a939cde41792dca38c549f0484 ] 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 Signed-off-by: Greg Kroah-Hartman --- net/batman-adv/bridge_loop_avoidance.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) --- 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 batad } /* 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); } /**