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[maint] batman-adv: Modify neigh_list only with rcu-list functions

Message ID 20160929152258.8217-1-sven.eckelmann@open-mesh.com
State Accepted, archived
Commit 0e384ddb1995ae400766cf33b95537fb115a7800
Delegated to: Sven Eckelmann
Headers show

Commit Message

Sven Eckelmann Sept. 29, 2016, 3:22 p.m. UTC
The batadv_hard_iface::neigh_list is accessed via rcu based primitives.
Thus all operations done on it have to fulfill the requirements by RCU. So
using non-RCU mechanisms like hlist_add_head is not allowed because it
misses the barriers required to protect concurrent readers when accessing
the data behind the pointer.

Fixes: fed2826b490c ("batman-adv: add list of unique single hop neighbors per hard-interface")
Signed-off-by: Sven Eckelmann <sven.eckelmann@open-mesh.com>
---
 net/batman-adv/originator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Linus Lüssing Oct. 6, 2016, 3:14 a.m. UTC | #1
On Thu, Sep 29, 2016 at 05:22:58PM +0200, Sven Eckelmann wrote:
> The batadv_hard_iface::neigh_list is accessed via rcu based primitives.
> Thus all operations done on it have to fulfill the requirements by RCU. So
> using non-RCU mechanisms like hlist_add_head is not allowed because it
> misses the barriers required to protect concurrent readers when accessing
> the data behind the pointer.
> 
> Fixes: fed2826b490c ("batman-adv: add list of unique single hop neighbors per hard-interface")
> Signed-off-by: Sven Eckelmann <sven.eckelmann@open-mesh.com>

Acked-by: Linus Lüssing <linus.luessing@c0d3.blue>
Sven Eckelmann Oct. 18, 2016, 11:32 a.m. UTC | #2
On Donnerstag, 29. September 2016 17:22:58 CEST Sven Eckelmann wrote:
> The batadv_hard_iface::neigh_list is accessed via rcu based primitives.
> Thus all operations done on it have to fulfill the requirements by RCU. So
> using non-RCU mechanisms like hlist_add_head is not allowed because it
> misses the barriers required to protect concurrent readers when accessing
> the data behind the pointer.
> 
> Fixes: fed2826b490c ("batman-adv: add list of unique single hop neighbors
> per hard-interface") Signed-off-by: Sven Eckelmann
> <sven.eckelmann@open-mesh.com>
> Acked-by: Linus Lüssing <linus.luessing@c0d3.blue>
> ---
>  net/batman-adv/originator.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied in 0e384ddb1995ae400766cf33b95537fb115a7800 [1].

Kind regards,
	Sven

[1] https://git.open-mesh.org/batman-adv.git/commit/0e384ddb1995ae400766cf33b95537fb115a7800
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Patch

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index 3940b5d..3e9667e 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -537,7 +537,7 @@  batadv_hardif_neigh_create(struct batadv_hard_iface *hard_iface,
 	if (bat_priv->algo_ops->neigh.hardif_init)
 		bat_priv->algo_ops->neigh.hardif_init(hardif_neigh);
 
-	hlist_add_head(&hardif_neigh->list, &hard_iface->neigh_list);
+	hlist_add_head_rcu(&hardif_neigh->list, &hard_iface->neigh_list);
 
 out:
 	spin_unlock_bh(&hard_iface->neigh_list_lock);