diff mbox series

[5/5] batman-adv: Prevent duplicated tvlv handler

Message ID 20180812190445.28013-6-sven@narfation.org (mailing list archive)
State Superseded, archived
Delegated to: Simon Wunderlich
Headers
Series batman-adv: Missing list checks for *list_add* |

Commit Message

Sven Eckelmann Aug. 12, 2018, 7:04 p.m. UTC 
  The function batadv_tvlv_handler_register is responsible for adding new
tvlv_handler to the handler_list. It first checks whether the entry
already is in the list or not. If it is, then the creation of a new entry
is aborted.

But the lock for the list is only held when the list is really modified.
This could lead to duplicated entries because another context could create
an entry with the same key between the check and the list manipulation.

The check and the manipulation of the list must therefore be in the same
locked code section.

Fixes: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/tvlv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Marek Lindner Sept. 6, 2018, 12:05 p.m. UTC | #1 
On Monday, 13 August 2018 03:04:45 HKT Sven Eckelmann wrote:
> The function batadv_tvlv_handler_register is responsible for adding new
> tvlv_handler to the handler_list. It first checks whether the entry
> already is in the list or not. If it is, then the creation of a new entry
> is aborted.
> 
> But the lock for the list is only held when the list is really modified.
> This could lead to duplicated entries because another context could create
> an entry with the same key between the check and the list manipulation.
> 
> The check and the manipulation of the list must therefore be in the same
> locked code section.
> 
> Fixes: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>


Acked-by: Marek Lindner <mareklindner@neomailbox.ch>

Cheers,
Marek
diff mbox series

Patch

diff --git a/net/batman-adv/tvlv.c b/net/batman-adv/tvlv.c
index a6374582..40e69c93 100644
--- a/net/batman-adv/tvlv.c
+++ b/net/batman-adv/tvlv.c
@@ -529,15 +529,20 @@  void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_handler *tvlv_handler;
 
+	spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
+
 	tvlv_handler = batadv_tvlv_handler_get(bat_priv, type, version);
 	if (tvlv_handler) {
+		spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
 		batadv_tvlv_handler_put(tvlv_handler);
 		return;
 	}
 
 	tvlv_handler = kzalloc(sizeof(*tvlv_handler), GFP_ATOMIC);
-	if (!tvlv_handler)
+	if (!tvlv_handler) {
+		spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
 		return;
+	}
 
 	tvlv_handler->ogm_handler = optr;
 	tvlv_handler->unicast_handler = uptr;
@@ -547,7 +552,6 @@  void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
 	kref_init(&tvlv_handler->refcount);
 	INIT_HLIST_NODE(&tvlv_handler->list);
 
-	spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
 	kref_get(&tvlv_handler->refcount);
 	hlist_add_head_rcu(&tvlv_handler->list, &bat_priv->tvlv.handler_list);
 	spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);