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 4.1-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-4.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Tue Jan 26 21:37:04 PST 2016 From: Sven Eckelmann <sven@xxxxxxxxxxxxx> Date: Thu, 14 Jan 2016 15:28:19 +0100 Subject: batman-adv: Avoid recursive call_rcu for batadv_bla_claim From: Sven Eckelmann <sven@xxxxxxxxxxxxx> [ 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@xxxxxxxxxxxxx> Acked-by: Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx> Signed-off-by: Marek Lindner <mareklindner@xxxxxxxxxxxxx> Signed-off-by: Antonio Quartulli <a@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -112,21 +112,17 @@ 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@xxxxxxxxxxxxx are queue-4.1/batman-adv-drop-immediate-batadv_neigh_node-free-function.patch queue-4.1/batman-adv-drop-immediate-neigh_ifinfo-free-function.patch queue-4.1/batman-adv-drop-immediate-orig_node-free-function.patch queue-4.1/batman-adv-drop-immediate-batadv_orig_ifinfo-free-function.patch queue-4.1/batman-adv-avoid-recursive-call_rcu-for-batadv_nc_node.patch queue-4.1/batman-adv-drop-immediate-batadv_hard_iface-free-function.patch queue-4.1/batman-adv-avoid-recursive-call_rcu-for-batadv_bla_claim.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html