[PATCH batadv v2 2/9] batman-adv: tp_meter: annotate last_recv_time access with READ/WRITE_ONCE

The last_recv_time field for batadv_tp_receiver tracks the jiffies value of
the most recent activity and is used to detect timeouts. These accesses are
not consistently protected by a lock, so READ_ONCE/WRITE_ONCE must be used
to prevent data races caused by compiler optimizations.

Fixes: 98d7a766b645 ("batman-adv: throughput meter implementation")
Signed-off-by: Sven Eckelmann <[email protected]>
---
 net/batman-adv/tp_meter.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c
index 259ac8c3..fb87fa14 100644
--- a/net/batman-adv/tp_meter.c
+++ b/net/batman-adv/tp_meter.c
@@ -1290,7 +1290,7 @@ static void batadv_tp_receiver_shutdown(struct timer_list *t)
 	bat_priv = tp_vars->common.bat_priv;
 
 	/* if there is recent activity rearm the timer */
-	if (!batadv_has_timed_out(tp_vars->last_recv_time,
+	if (!batadv_has_timed_out(READ_ONCE(tp_vars->last_recv_time),
 				  BATADV_TP_RECV_TIMEOUT)) {
 		/* reset the receiver shutdown timer */
 		batadv_tp_reset_receiver_timer(tp_vars);
@@ -1532,7 +1532,7 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
 	tp_vars = batadv_tp_list_find_receiver_session(bat_priv, icmp->orig,
 						       icmp->session);
 	if (tp_vars) {
-		tp_vars->last_recv_time = jiffies;
+		WRITE_ONCE(tp_vars->last_recv_time, jiffies);
 		goto out_unlock;
 	}
 
@@ -1562,7 +1562,7 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
 	kref_get(&tp_vars->common.refcount);
 	timer_setup(&tp_vars->common.timer, batadv_tp_receiver_shutdown, 0);
 
-	tp_vars->last_recv_time = jiffies;
+	WRITE_ONCE(tp_vars->last_recv_time, jiffies);
 
 	kref_get(&tp_vars->common.refcount);
 	hlist_add_head_rcu(&tp_vars->common.list, &bat_priv->tp_receiver_list);
@@ -1613,7 +1613,7 @@ static void batadv_tp_recv_msg(struct batadv_priv *bat_priv,
 			goto out;
 		}
 
-		tp_vars->last_recv_time = jiffies;
+		WRITE_ONCE(tp_vars->last_recv_time, jiffies);
 	}
 
 	/* if the packet is a duplicate, it may be the case that an ACK has been

-- 
2.47.3