batman-adv: Avoid race in TT TVLV allocator helper

ecsv · simonwunderlich · commit 8ba0f9bd3bde · 2018-05-10T16:08:54.000+02:00
The functions batadv_tt_prepare_tvlv_local_data and batadv_tt_prepare_tvlv_global_data are responsible for preparing a buffer which can be used to store the TVLV container for TT and add the VLAN information to it. This will be done in three phases: 1. count the number of VLANs and their entries 2. allocate the buffer using the counters from the previous step and limits from the caller (parameter tt_len) 3. insert the VLAN information to the buffer The step 1 and 3 operate on a list which contains the VLANs. The access to these lists must be protected with an appropriate lock or otherwise they might operate on on different entries. This could for example happen when another context is adding VLAN entries to this list. This could lead to a buffer overflow in these functions when enough entries were added between step 1 and 3 to the VLAN lists that the buffer room for the entries (*tt_change) is smaller then the now required extra buffer for new VLAN entries. Fixes: 7ea7b4a ("batman-adv: make the TT CRC logic VLAN specific") Signed-off-by: Sven Eckelmann <sven@narfation.org> Acked-by: Antonio Quartulli <a@unstable.cc> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
@@ -862,7 +862,7 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	struct batadv_orig_node_vlan *vlan;
 	u8 *tt_change_ptr;
 
-	rcu_read_lock();
+	spin_lock_bh(&orig_node->vlan_list_lock);
 	hlist_for_each_entry_rcu(vlan, &orig_node->vlan_list, list) {
 		num_vlan++;
 		num_entries += atomic_read(&vlan->tt.num_entries);
@@ -900,7 +900,7 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	*tt_change = (struct batadv_tvlv_tt_change *)tt_change_ptr;
 
 out:
-	rcu_read_unlock();
+	spin_unlock_bh(&orig_node->vlan_list_lock);
 	return tvlv_len;
 }
 
@@ -936,7 +936,7 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	u8 *tt_change_ptr;
 	int change_offset;
 
-	rcu_read_lock();
+	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
 	hlist_for_each_entry_rcu(vlan, &bat_priv->softif_vlan_list, list) {
 		num_vlan++;
 		num_entries += atomic_read(&vlan->tt.num_entries);
@@ -974,7 +974,7 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	*tt_change = (struct batadv_tvlv_tt_change *)tt_change_ptr;
 
 out:
-	rcu_read_unlock();
+	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
 	return tvlv_len;
 }
 
