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 4.4-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_bla_claim.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 <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Jan 26 21:31:27 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
@@ -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@xxxxxxxxxxxxx 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
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