diff mbox

[maint,1/2] batman-adv: Only put gw_node list reference when removed

Message ID 1454243280-15126-1-git-send-email-sven@narfation.org (mailing list archive)
State Accepted, archived
Commit c215e4e249753acec3e4b8614623132a2f28671f
Headers

Commit Message

Sven Eckelmann Jan. 31, 2016, 12:27 p.m. UTC 
  The batadv_gw_node reference counter in batadv_gw_node_update can only be
reduced when the list entry was actually removed. Otherwise the reference
counter may reach zero when batadv_gw_node_update is called from two
different contexts for the same gw_node but only one context is actually
removing the entry from the list.

The release function for this gw_node is not called inside the list_lock
spinlock protected region because the function batadv_gw_node_update still
holds a gw_node reference for the object pointer on the stack. Thus the
actual release function (when required) will be called only at the end of
the function.

Fixes: 0511575c4d03 ("batman-adv: remove obsolete deleted attribute for gateway node")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/gateway_client.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Marek Lindner Feb. 10, 2016, 10:43 a.m. UTC | #1 
On Sunday, January 31, 2016 13:27:59 Sven Eckelmann wrote:
> The batadv_gw_node reference counter in batadv_gw_node_update can only be
> reduced when the list entry was actually removed. Otherwise the reference
> counter may reach zero when batadv_gw_node_update is called from two
> different contexts for the same gw_node but only one context is actually
> removing the entry from the list.
> 
> The release function for this gw_node is not called inside the list_lock
> spinlock protected region because the function batadv_gw_node_update still
> holds a gw_node reference for the object pointer on the stack. Thus the
> actual release function (when required) will be called only at the end of
> the function.
> 
> Fixes: 0511575c4d03 ("batman-adv: remove obsolete deleted attribute for
> gateway node") Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
>  net/batman-adv/gateway_client.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

Applied in revision c215e4e.

Thanks,
Marek
Marek Lindner Feb. 10, 2016, 10:45 a.m. UTC | #2 
On Sunday, January 31, 2016 13:28:00 Sven Eckelmann wrote:
> The batadv_orig_node_vlan reference counter in batadv_tt_global_size_mod
> can only be reduced when the list entry was actually removed. Otherwise the
> reference counter may reach zero when batadv_tt_global_size_mod is called
> from two different contexts for the same orig_node_vlan but only one
> context is actually removing the entry from the list.
> 
> The release function for this orig_node_vlan is not called inside the
> vlan_list_lock spinlock protected region because the function
> batadv_tt_global_size_mod still holds a orig_node_vlan reference for the
> object pointer on the stack. Thus the actual release function (when
> required) will be called only at the end of the function.
> 
> Fixes: 21a57f6e7a3b ("batman-adv: make the TT CRC logic VLAN specific")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
>  net/batman-adv/translation-table.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Applied in revision ead9389.

Thanks,
Marek
diff mbox

Patch

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 8350775..c9b8b48 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -527,11 +527,12 @@  void batadv_gw_node_update(struct batadv_priv *bat_priv,
 		 * gets dereferenced.
 		 */
 		spin_lock_bh(&bat_priv->gw.list_lock);
-		hlist_del_init_rcu(&gw_node->list);
+		if (!hlist_unhashed(&gw_node->list)) {
+			hlist_del_init_rcu(&gw_node->list);
+			batadv_gw_node_free_ref(gw_node);
+		}
 		spin_unlock_bh(&bat_priv->gw.list_lock);
 
-		batadv_gw_node_free_ref(gw_node);
-
 		curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 		if (gw_node == curr_gw)
 			batadv_gw_reselect(bat_priv);