[PATCH net-next 12/15] batman-adv: bla: annotate lasttime access with READ/WRITE_ONCE

[Simon Wunderlich <sw@simonwunderlich.de>]

From: Sven Eckelmann <sven@narfation.org>

The lasttime field for claim, backbone_gw, and loopdetect 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.

Cc: stable@kernel.org
Fixes: 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/bridge_loop_avoidance.c | 28 +++++++++++++-------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 87d6b11161e4a..0461f11227d06 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -513,7 +513,7 @@ batadv_bla_get_backbone_gw(struct batadv_priv *bat_priv, const u8 *orig,
 		return NULL;
 
 	entry->vid = vid;
-	entry->lasttime = jiffies;
+	WRITE_ONCE(entry->lasttime, jiffies);
 	entry->crc = BATADV_BLA_CRC_INIT;
 	entry->bat_priv = bat_priv;
 	spin_lock_init(&entry->crc_lock);
@@ -581,7 +581,7 @@ batadv_bla_update_own_backbone_gw(struct batadv_priv *bat_priv,
 	if (unlikely(!backbone_gw))
 		return;
 
-	backbone_gw->lasttime = jiffies;
+	WRITE_ONCE(backbone_gw->lasttime, jiffies);
 	batadv_backbone_gw_put(backbone_gw);
 }
 
@@ -715,7 +715,7 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv,
 		ether_addr_copy(claim->addr, mac);
 		spin_lock_init(&claim->backbone_lock);
 		claim->vid = vid;
-		claim->lasttime = jiffies;
+		WRITE_ONCE(claim->lasttime, jiffies);
 		kref_get(&backbone_gw->refcount);
 		claim->backbone_gw = backbone_gw;
 		kref_init(&claim->refcount);
@@ -737,7 +737,7 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv,
 			return;
 		}
 	} else {
-		claim->lasttime = jiffies;
+		WRITE_ONCE(claim->lasttime, jiffies);
 		if (claim->backbone_gw == backbone_gw)
 			/* no need to register a new backbone */
 			goto claim_free_ref;
@@ -770,7 +770,7 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv,
 	spin_lock_bh(&backbone_gw->crc_lock);
 	backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN);
 	spin_unlock_bh(&backbone_gw->crc_lock);
-	backbone_gw->lasttime = jiffies;
+	WRITE_ONCE(backbone_gw->lasttime, jiffies);
 
 claim_free_ref:
 	batadv_claim_put(claim);
@@ -859,7 +859,7 @@ static bool batadv_handle_announce(struct batadv_priv *bat_priv, u8 *an_addr,
 		return true;
 
 	/* handle as ANNOUNCE frame */
-	backbone_gw->lasttime = jiffies;
+	WRITE_ONCE(backbone_gw->lasttime, jiffies);
 	crc = ntohs(*((__force __be16 *)(&an_addr[4])));
 
 	batadv_dbg(BATADV_DBG_BLA, bat_priv,
@@ -1254,7 +1254,7 @@ static void batadv_bla_purge_backbone_gw(struct batadv_priv *bat_priv, int now)
 						  head, hash_entry) {
 				if (now)
 					goto purge_now;
-				if (!batadv_has_timed_out(backbone_gw->lasttime,
+				if (!batadv_has_timed_out(READ_ONCE(backbone_gw->lasttime),
 							  BATADV_BLA_BACKBONE_TIMEOUT))
 					continue;
 
@@ -1335,7 +1335,7 @@ static void batadv_bla_purge_claims(struct batadv_priv *bat_priv,
 						primary_if->net_dev->dev_addr))
 				goto skip;
 
-			if (!batadv_has_timed_out(claim->lasttime,
+			if (!batadv_has_timed_out(READ_ONCE(claim->lasttime),
 						  BATADV_BLA_CLAIM_TIMEOUT))
 				goto skip;
 
@@ -1495,7 +1495,7 @@ static void batadv_bla_periodic_work(struct work_struct *work)
 		eth_random_addr(bat_priv->bla.loopdetect_addr);
 		bat_priv->bla.loopdetect_addr[0] = 0xba;
 		bat_priv->bla.loopdetect_addr[1] = 0xbe;
-		bat_priv->bla.loopdetect_lasttime = jiffies;
+		WRITE_ONCE(bat_priv->bla.loopdetect_lasttime, jiffies);
 		atomic_set(&bat_priv->bla.loopdetect_next,
 			   BATADV_BLA_LOOPDETECT_PERIODS);
 
@@ -1516,7 +1516,7 @@ static void batadv_bla_periodic_work(struct work_struct *work)
 						primary_if->net_dev->dev_addr))
 				continue;
 
-			backbone_gw->lasttime = jiffies;
+			WRITE_ONCE(backbone_gw->lasttime, jiffies);
 
 			batadv_bla_send_announce(bat_priv, backbone_gw);
 			if (send_loopdetect)
@@ -1900,7 +1900,7 @@ batadv_bla_loopdetect_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	/* If the packet came too late, don't forward it on the mesh
 	 * but don't consider that as loop. It might be a coincidence.
 	 */
-	if (batadv_has_timed_out(bat_priv->bla.loopdetect_lasttime,
+	if (batadv_has_timed_out(READ_ONCE(bat_priv->bla.loopdetect_lasttime),
 				 BATADV_BLA_LOOPDETECT_TIMEOUT))
 		return true;
 
@@ -2015,7 +2015,7 @@ bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb,
 
 	if (own_claim) {
 		/* ... allow it in any case */
-		claim->lasttime = jiffies;
+		WRITE_ONCE(claim->lasttime, jiffies);
 		goto allow;
 	}
 
@@ -2117,7 +2117,7 @@ bool batadv_bla_tx(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		/* if yes, the client has roamed and we have
 		 * to unclaim it.
 		 */
-		if (batadv_has_timed_out(claim->lasttime, 100)) {
+		if (batadv_has_timed_out(READ_ONCE(claim->lasttime), 100)) {
 			/* only unclaim if the last claim entry is
 			 * older than 100 ms to make sure we really
 			 * have a roaming client here.
@@ -2362,7 +2362,7 @@ batadv_bla_backbone_dump_entry(struct sk_buff *msg, u32 portid,
 	backbone_crc = backbone_gw->crc;
 	spin_unlock_bh(&backbone_gw->crc_lock);
 
-	msecs = jiffies_to_msecs(jiffies - backbone_gw->lasttime);
+	msecs = jiffies_to_msecs(jiffies - READ_ONCE(backbone_gw->lasttime));
 
 	if (is_own)
 		if (nla_put_flag(msg, BATADV_ATTR_BLA_OWN)) {
-- 
2.47.3