[PATCH net 01/20] can: j1939: use netdevice_tracker for j1939_{priv,session,ecu} tracking
From: Marc Kleine-Budde <mkl@pengutronix.de>
Date: 2026-07-29 10:29:35
Also in:
linux-can
Subsystem:
can network layer, can-j1939 network layer, the rest · Maintainers:
Oliver Hartkopp, Marc Kleine-Budde, Robin van der Gracht, Oleksij Rempel, Linus Torvalds
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
syzbot is still reporting
unregister_netdevice: waiting for vcan0 to become free. Usage count = 2
problem. A debug printk() patch in linux-next-20260508 identified that
there is dev_hold()/dev_put() imbalance in j1939_priv management.
Call trace for vcan0[26] +4 at
__dev_hold include/linux/netdevice.h:4470 [inline]
netdev_hold include/linux/netdevice.h:4513 [inline]
dev_hold include/linux/netdevice.h:4536 [inline]
j1939_priv_create net/can/j1939/main.c:140 [inline]
j1939_netdev_start+0x36b/0xc10 net/can/j1939/main.c:268
j1939_sk_bind+0x853/0xb30 net/can/j1939/socket.c:506
__sys_bind_socket net/socket.c:1948 [inline]
__sys_bind+0x2e9/0x410 net/socket.c:1979
Call trace for vcan0[28] -3 at
__dev_put include/linux/netdevice.h:4456 [inline]
netdev_put include/linux/netdevice.h:4523 [inline]
dev_put include/linux/netdevice.h:4548 [inline]
__j1939_priv_release net/can/j1939/main.c:166 [inline]
kref_put include/linux/kref.h:65 [inline]
j1939_priv_put+0x128/0x270 net/can/j1939/main.c:172
j1939_sk_sock_destruct+0x52/0x90 net/can/j1939/socket.c:388
__sk_destruct+0x8d/0x9d0 net/core/sock.c:2352
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core kernel/rcu/tree.c:2869 [inline]
rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957
smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
This refcount leak in j1939_priv might be caused by a refcount leak in
j1939_{session,ecu} because j1939_{session,ecu} holds a ref on j1939_priv.
For further investigation using upstream kernels, enable netdevice_tracker
in j1939_{priv,session,ecu} management.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20260728055835.1151785-2-o.rempel@pengutronix.de
Cc: stable@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
net/can/j1939/bus.c | 2 ++
net/can/j1939/j1939-priv.h | 3 +++
net/can/j1939/main.c | 8 ++++----
net/can/j1939/transport.c | 2 ++
4 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/net/can/j1939/bus.c b/net/can/j1939/bus.c
index dc374286eeb6..cdc3c0a71937 100644
--- a/net/can/j1939/bus.c
+++ b/net/can/j1939/bus.c@@ -20,6 +20,7 @@ static void __j1939_ecu_release(struct kref *kref) struct j1939_priv *priv = ecu->priv; list_del(&ecu->list); + netdev_put(priv->ndev, &ecu->priv_dev_tracker); kfree(ecu); j1939_priv_put(priv); }
@@ -155,6 +156,7 @@ struct j1939_ecu *j1939_ecu_create_locked(struct j1939_priv *priv, name_t name) if (!ecu) return ERR_PTR(-ENOMEM); kref_init(&ecu->kref); + netdev_hold(priv->ndev, &ecu->priv_dev_tracker, gfp_any()); ecu->addr = J1939_IDLE_ADDR; ecu->name = name;
diff --git a/net/can/j1939/j1939-priv.h b/net/can/j1939/j1939-priv.h
index 81f58924b4ac..cf26352d1d8c 100644
--- a/net/can/j1939/j1939-priv.h
+++ b/net/can/j1939/j1939-priv.h@@ -38,6 +38,7 @@ struct j1939_ecu { struct hrtimer ac_timer; struct kref kref; struct j1939_priv *priv; + netdevice_tracker priv_dev_tracker; /* count users, to help transport protocol decide for interaction */ int nusers;
@@ -60,6 +61,7 @@ struct j1939_priv { rwlock_t lock; struct net_device *ndev; + netdevice_tracker dev_tracker; /* list of 256 ecu ptrs, that cache the claimed addresses. * also protected by the above lock
@@ -230,6 +232,7 @@ enum j1939_session_state { struct j1939_session { struct j1939_priv *priv; + netdevice_tracker priv_dev_tracker; struct list_head active_session_list_entry; struct list_head sk_session_queue_entry; struct kref kref;
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index 9937c04241bc..5e5e6c228f22 100644
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c@@ -137,7 +137,7 @@ static struct j1939_priv *j1939_priv_create(struct net_device *ndev) priv->ndev = ndev; kref_init(&priv->kref); kref_init(&priv->rx_kref); - dev_hold(ndev); + netdev_hold(ndev, &priv->dev_tracker, GFP_KERNEL); netdev_dbg(priv->ndev, "%s : 0x%p\n", __func__, priv);
@@ -163,7 +163,7 @@ static void __j1939_priv_release(struct kref *kref) WARN_ON_ONCE(!list_empty(&priv->ecus)); WARN_ON_ONCE(!list_empty(&priv->j1939_socks)); - dev_put(ndev); + netdev_put(ndev, &priv->dev_tracker); kfree(priv); }
@@ -281,7 +281,7 @@ struct j1939_priv *j1939_netdev_start(struct net_device *ndev) */ kref_get(&priv_new->rx_kref); mutex_unlock(&j1939_netdev_lock); - dev_put(ndev); + netdev_put(ndev, &priv->dev_tracker); kfree(priv); return priv_new; }
@@ -298,7 +298,7 @@ struct j1939_priv *j1939_netdev_start(struct net_device *ndev) j1939_priv_set(ndev, NULL); mutex_unlock(&j1939_netdev_lock); - dev_put(ndev); + netdev_put(ndev, &priv->dev_tracker); kfree(priv); return ERR_PTR(ret);
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 8a31cb23bc76..98f96362b20f 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c@@ -283,6 +283,7 @@ static void j1939_session_destroy(struct j1939_session *session) kfree_skb(skb); } __j1939_session_drop(session); + netdev_put(session->priv->ndev, &session->priv_dev_tracker); j1939_priv_put(session->priv); kfree(session); }
@@ -1526,6 +1527,7 @@ static struct j1939_session *j1939_session_new(struct j1939_priv *priv, INIT_LIST_HEAD(&session->active_session_list_entry); INIT_LIST_HEAD(&session->sk_session_queue_entry); kref_init(&session->kref); + netdev_hold(priv->ndev, &session->priv_dev_tracker, gfp_any()); j1939_priv_get(priv); session->priv = priv;
base-commit: 3bd438a58e910db5dc369aa25dfed1fc95f1b596 -- 2.53.0