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")
Reported-by: syzbot+bfab43087ad57222ce96@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/695e3d74.050a0220.1c677c.035f.GAE@google.com/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260108093806.834459-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 18 insertions, 14 deletions

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 58d22e2b85fc..0501ffcb8a3d 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;
 		}
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 777fa869c1a1..e355a15bf5ab 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -221,8 +221,8 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 		if (test_bit(BR_FDB_LOCAL, &dst->flags))
 			return br_pass_frame_up(skb, false);
 
-		if (now != dst->used)
-			dst->used = now;
+		if (now != READ_ONCE(dst->used))
+			WRITE_ONCE(dst->used, now);
 		br_forward(dst->dst, skb, local_rcv, false);
 	} else {
 		if (!mcast_hit)