[PATCH 6.6 012/254] net: bridge: annotate data-races around fdb->{updated,used}

Greg Kroah-Hartman
2026-01-28T15:25:11Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit b25a0b4a2193407aa72a4cd1df66a7ed07dd4f1e ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/bridge/br_fdb.c | 28 ++++++++++++++++------------
net/bridge/br_input.c | 4 ++--
2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 91903076d30bd..fa2970db21301 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -73,7 +73,7 @@ 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 void fdb_rcu_free(struct rcu_head *head)
@@ -136,9 +136,9 @@ 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;
@@ -534,7 +534,7 @@ 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)) {
@@ -792,6 +792,7 @@ 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));
@@ -821,8 +822,11 @@ 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;
}
@@ -870,8 +874,8 @@ 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);
}

@@ -1103,10 +1107,10 @@ 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);
}

@@ -1419,7 +1423,7 @@ 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);
@@ -1428,7 +1432,7 @@ 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 951330c1a813b..2d5b81ebbaa6d 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -207,8 +207,8 @@ 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)
--
2.51.0