Patch "batman-adv: Avoid recursive call_rcu for batadv_bla_claim" has been added to the 4.3-stable tree

Patch "batman-adv: Avoid recursive call_rcu for batadv_bla_claim" has been added to the 4.3-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    batman-adv: Avoid recursive call_rcu for batadv_bla_claim

to the 4.3-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_bla_claim.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Tue Jan 26 21:35:03 PST 2016
From: Sven Eckelmann <sven@narfation.org>
Date: Thu, 14 Jan 2016 15:28:19 +0100
Subject: batman-adv: Avoid recursive call_rcu for batadv_bla_claim

From: Sven Eckelmann <sven@narfation.org>

[ 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 <sven@narfation.org>
Acked-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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);
 }
 
 /**


Patches currently in stable-queue which might be from sven@narfation.org are

queue-4.3/batman-adv-drop-immediate-batadv_neigh_node-free-function.patch
queue-4.3/batman-adv-drop-immediate-neigh_ifinfo-free-function.patch
queue-4.3/batman-adv-drop-immediate-orig_node-free-function.patch
queue-4.3/batman-adv-drop-immediate-batadv_orig_ifinfo-free-function.patch
queue-4.3/batman-adv-avoid-recursive-call_rcu-for-batadv_nc_node.patch
queue-4.3/batman-adv-drop-immediate-batadv_hard_iface-free-function.patch
queue-4.3/batman-adv-avoid-recursive-call_rcu-for-batadv_bla_claim.patch