netdev - [PATCH v2 net] net: bridge: annotate data-races around fdb->{updated,used}

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Message-ID: <20260107083219.3219130-1-edumazet@google.com>
Date: Wed,  7 Jan 2026 08:32:19 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Nikolay Aleksandrov <razor@...ckwall.org>
Subject: [PATCH v2 net] net: bridge: annotate data-races around fdb->{updated,used}

fdb->updated and fdb->used are read and written locklessly.

Add READ_ONCE()/WRITE_ONCE() annotations.

Fixes: 31cbc39b6344 ("net: bridge: add option to allow activity notifications for any fdb entries")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Nikolay Aleksandrov <razor@...ckwall.org>
---
v2: annotate all problematic fdb->updated and fdb->used reads/writes.
v1: https://lore.kernel.org/netdev/CANn89iL8-e_jphcg49eX=zdWrOeuA-AJDL0qhsTrApA4YnOFEg@mail.gmail.com/T/#mf99b76469697813939abe745f42ace3e201ef6f4

 net/bridge/br_fdb.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 58d22e2b85fc3551bd5aec9c20296ddfcecaa040..0501ffcb8a3ddb21a19254915564b4000b6b6911 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -70,7 +70,7 @@ static inline int has_expired(const struct net_bridge *br,
 {
 	return !test_bit(BR_FDB_STATIC, &fdb->flags) &&
 	       !test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags) &&
-	       time_before_eq(fdb->updated + hold_time(br), jiffies);
+	       time_before_eq(READ_ONCE(fdb->updated) + hold_time(br), jiffies);
 }
 
 static int fdb_to_nud(const struct net_bridge *br,
@@ -126,9 +126,9 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
 	if (nla_put_u32(skb, NDA_FLAGS_EXT, ext_flags))
 		goto nla_put_failure;
 
-	ci.ndm_used	 = jiffies_to_clock_t(now - fdb->used);
+	ci.ndm_used	 = jiffies_to_clock_t(now - READ_ONCE(fdb->used));
 	ci.ndm_confirmed = 0;
-	ci.ndm_updated	 = jiffies_to_clock_t(now - fdb->updated);
+	ci.ndm_updated	 = jiffies_to_clock_t(now - READ_ONCE(fdb->updated));
 	ci.ndm_refcnt	 = 0;
 	if (nla_put(skb, NDA_CACHEINFO, sizeof(ci), &ci))
 		goto nla_put_failure;
@@ -551,7 +551,7 @@ void br_fdb_cleanup(struct work_struct *work)
 	 */
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(f, &br->fdb_list, fdb_node) {
-		unsigned long this_timer = f->updated + delay;
+		unsigned long this_timer = READ_ONCE(f->updated) + delay;
 
 		if (test_bit(BR_FDB_STATIC, &f->flags) ||
 		    test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &f->flags)) {
@@ -924,6 +924,7 @@ int br_fdb_fillbuf(struct net_bridge *br, void *buf,
 {
 	struct net_bridge_fdb_entry *f;
 	struct __fdb_entry *fe = buf;
+	unsigned long delta;
 	int num = 0;
 
 	memset(buf, 0, maxnum*sizeof(struct __fdb_entry));
@@ -953,8 +954,11 @@ int br_fdb_fillbuf(struct net_bridge *br, void *buf,
 		fe->port_hi = f->dst->port_no >> 8;
 
 		fe->is_local = test_bit(BR_FDB_LOCAL, &f->flags);
-		if (!test_bit(BR_FDB_STATIC, &f->flags))
-			fe->ageing_timer_value = jiffies_delta_to_clock_t(jiffies - f->updated);
+		if (!test_bit(BR_FDB_STATIC, &f->flags)) {
+			delta = jiffies - READ_ONCE(f->updated);
+			fe->ageing_timer_value =
+				jiffies_delta_to_clock_t(delta);
+		}
 		++fe;
 		++num;
 	}
@@ -1002,8 +1006,8 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
 			unsigned long now = jiffies;
 			bool fdb_modified = false;
 
-			if (now != fdb->updated) {
-				fdb->updated = now;
+			if (now != READ_ONCE(fdb->updated)) {
+				WRITE_ONCE(fdb->updated, now);
 				fdb_modified = __fdb_mark_active(fdb);
 			}
 
@@ -1242,10 +1246,10 @@ static int fdb_add_entry(struct net_bridge *br, struct net_bridge_port *source,
 	if (fdb_handle_notify(fdb, notify))
 		modified = true;
 
-	fdb->used = jiffies;
+	WRITE_ONCE(fdb->used, jiffies);
 	if (modified) {
 		if (refresh)
-			fdb->updated = jiffies;
+			WRITE_ONCE(fdb->updated, jiffies);
 		fdb_notify(br, fdb, RTM_NEWNEIGH, true);
 	}
 
@@ -1556,7 +1560,7 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
 			goto err_unlock;
 		}
 
-		fdb->updated = jiffies;
+		WRITE_ONCE(fdb->updated, jiffies);
 
 		if (READ_ONCE(fdb->dst) != p) {
 			WRITE_ONCE(fdb->dst, p);
@@ -1565,7 +1569,7 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
 
 		if (test_and_set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
 			/* Refresh entry */
-			fdb->used = jiffies;
+			WRITE_ONCE(fdb->used, jiffies);
 		} else {
 			modified = true;
 		}
-- 
2.52.0.351.gbe84eed79e-goog