From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43073 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753919AbcA0GgY (ORCPT ); Wed, 27 Jan 2016 01:36:24 -0500 Subject: Patch "batman-adv: Avoid recursive call_rcu for batadv_nc_node" has been added to the 4.4-stable tree To: sven@narfation.org, a@unstable.cc, gregkh@linuxfoundation.org, mareklindner@neomailbox.ch Cc: , From: Date: Tue, 26 Jan 2016 22:30:01 -0800 Message-ID: <145387620123989@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled batman-adv: Avoid recursive call_rcu for batadv_nc_node to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: batman-adv-avoid-recursive-call_rcu-for-batadv_nc_node.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Tue Jan 26 21:31:27 PST 2016 From: Sven Eckelmann Date: Tue, 5 Jan 2016 12:06:19 +0100 Subject: batman-adv: Avoid recursive call_rcu for batadv_nc_node From: Sven Eckelmann [ Upstream commit 44e8e7e91d6c7c7ab19688750f7257292640d1a0 ] The batadv_nc_node_free_ref function uses call_rcu to delay the free of the batadv_nc_node 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_nc_node also contains a reference to orig_node which must be removed. The reference drop of orig_node was done in the call_rcu function batadv_nc_node_free_rcu but should actually be done in the batadv_nc_node_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: d56b1705e28c ("batman-adv: network coding - detect coding nodes and remove these after timeout") Signed-off-by: Sven Eckelmann Signed-off-by: Marek Lindner Signed-off-by: Antonio Quartulli Signed-off-by: Greg Kroah-Hartman --- net/batman-adv/network-coding.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) --- a/net/batman-adv/network-coding.c +++ b/net/batman-adv/network-coding.c @@ -203,28 +203,25 @@ void batadv_nc_init_orig(struct batadv_o } /** - * batadv_nc_node_free_rcu - rcu callback to free an nc node and remove - * its refcount on the orig_node - * @rcu: rcu pointer of the nc node + * batadv_nc_node_release - release nc_node from lists and queue for free after + * rcu grace period + * @nc_node: the nc node to free */ -static void batadv_nc_node_free_rcu(struct rcu_head *rcu) +static void batadv_nc_node_release(struct batadv_nc_node *nc_node) { - struct batadv_nc_node *nc_node; - - nc_node = container_of(rcu, struct batadv_nc_node, rcu); batadv_orig_node_free_ref(nc_node->orig_node); - kfree(nc_node); + kfree_rcu(nc_node, rcu); } /** - * batadv_nc_node_free_ref - decrements the nc node refcounter and possibly - * frees it + * batadv_nc_node_free_ref - decrement the nc node refcounter and possibly + * release it * @nc_node: the nc node to free */ static void batadv_nc_node_free_ref(struct batadv_nc_node *nc_node) { if (atomic_dec_and_test(&nc_node->refcount)) - call_rcu(&nc_node->rcu, batadv_nc_node_free_rcu); + batadv_nc_node_release(nc_node); } /** Patches currently in stable-queue which might be from sven@narfation.org are queue-4.4/batman-adv-drop-immediate-batadv_neigh_node-free-function.patch queue-4.4/batman-adv-drop-immediate-neigh_ifinfo-free-function.patch queue-4.4/batman-adv-drop-immediate-orig_node-free-function.patch queue-4.4/batman-adv-drop-immediate-batadv_orig_ifinfo-free-function.patch queue-4.4/batman-adv-avoid-recursive-call_rcu-for-batadv_nc_node.patch queue-4.4/batman-adv-drop-immediate-batadv_hard_iface-free-function.patch queue-4.4/batman-adv-avoid-recursive-call_rcu-for-batadv_bla_claim.patch