[PATCH 5.15 08/25] batman-adv: tp_meter: add only finished tp_vars to lists

[Sven Eckelmann <sven@narfation.org>]

commit 15ccbf685222274f5add1387af58c2a41a95f81e upstream.

When the receiver variables (aka "session") are initialized, then they are
added to the list of sessions before the timer is set up. A RCU protected
reader could therefore find the entry and run mod_setup before
batadv_tp_init_recv() finished the timer initialization.

The same is true for batadv_tp_start(), which must first initialize the
finish_work and the test_length to avoid a similar problem.

Cc: stable@kernel.org
Fixes: 33a3bb4a3345 ("batman-adv: throughput meter implementation")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/tp_meter.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c
index 7385cd02abf9f..257f8d042d158 100644
--- a/net/batman-adv/tp_meter.c
+++ b/net/batman-adv/tp_meter.c
@@ -1096,21 +1096,21 @@ void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
 	tp_vars->prerandom_offset = 0;
 	spin_lock_init(&tp_vars->prerandom_lock);
 
-	kref_get(&tp_vars->refcount);
-	hlist_add_head_rcu(&tp_vars->list, &bat_priv->tp_list);
-	spin_unlock_bh(&bat_priv->tp_list_lock);
-
 	tp_vars->test_length = test_length;
 	if (!tp_vars->test_length)
 		tp_vars->test_length = BATADV_TP_DEF_TEST_LENGTH;
 
+	/* init work item for finished tp tests */
+	INIT_DELAYED_WORK(&tp_vars->finish_work, batadv_tp_sender_finish);
+
+	kref_get(&tp_vars->refcount);
+	hlist_add_head_rcu(&tp_vars->list, &bat_priv->tp_list);
+	spin_unlock_bh(&bat_priv->tp_list_lock);
+
 	batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
 		   "Meter: starting throughput meter towards %pM (length=%ums)\n",
 		   dst, test_length);
 
-	/* init work item for finished tp tests */
-	INIT_DELAYED_WORK(&tp_vars->finish_work, batadv_tp_sender_finish);
-
 	/* start tp kthread. This way the write() call issued from userspace can
 	 * happily return and avoid to block
 	 */
@@ -1430,10 +1430,10 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
 	INIT_LIST_HEAD(&tp_vars->unacked_list);
 
 	kref_get(&tp_vars->refcount);
-	hlist_add_head_rcu(&tp_vars->list, &bat_priv->tp_list);
+	timer_setup(&tp_vars->timer, batadv_tp_receiver_shutdown, 0);
 
 	kref_get(&tp_vars->refcount);
-	timer_setup(&tp_vars->timer, batadv_tp_receiver_shutdown, 0);
+	hlist_add_head_rcu(&tp_vars->list, &bat_priv->tp_list);
 
 	batadv_tp_reset_receiver_timer(tp_vars);
 
-- 
2.47.3