[PATCH v12 net-next 3/5] psp: add a new netdev event for dev unregister

Wei Wang
2026-05-01T17:55:50Z

Add a new netdev event for dev unregister and handle the removal of this
dev from psp->assoc_dev_list, upon the first dev-assoc operation.

Signed-off-by: Wei Wang <weibunny@fb.com>
Reviewed-by: Daniel Zahka <daniel.zahka@gmail.com>
---
Documentation/netlink/specs/psp.yaml | 2 +-
net/psp/psp-nl-gen.c | 2 +-
net/psp/psp-nl-gen.h | 3 ++
net/psp/psp.h | 1 +
net/psp/psp_main.c | 76 ++++++++++++++++++++++++++++
net/psp/psp_nl.c | 29 +++++++++++
6 files changed, 111 insertions(+), 2 deletions(-)

diff --git a/Documentation/netlink/specs/psp.yaml b/Documentation/netlink/specs/psp.yaml
index 3d1b7223e084..538ed9184965 100644
--- a/Documentation/netlink/specs/psp.yaml
+++ b/Documentation/netlink/specs/psp.yaml
@@ -328,7 +328,7 @@ operations:
- nsid
reply:
attributes: []
- pre: psp-device-get-locked
+ pre: psp-device-get-locked-dev-assoc
post: psp-device-unlock
-
name: dev-disassoc
diff --git a/net/psp/psp-nl-gen.c b/net/psp/psp-nl-gen.c
index 114299c64423..389a8480cc3d 100644
--- a/net/psp/psp-nl-gen.c
+++ b/net/psp/psp-nl-gen.c
@@ -135,7 +135,7 @@ static const struct genl_split_ops psp_nl_ops[] = {
},
{
.cmd = PSP_CMD_DEV_ASSOC,
- .pre_doit = psp_device_get_locked,
+ .pre_doit = psp_device_get_locked_dev_assoc,
.doit = psp_nl_dev_assoc_doit,
.post_doit = psp_device_unlock,
.policy = psp_dev_assoc_nl_policy,
diff --git a/net/psp/psp-nl-gen.h b/net/psp/psp-nl-gen.h
index 4dd0f0f23053..24d51bff997f 100644
--- a/net/psp/psp-nl-gen.h
+++ b/net/psp/psp-nl-gen.h
@@ -21,6 +21,9 @@ int psp_device_get_locked_admin(const struct genl_split_ops *ops,
struct sk_buff *skb, struct genl_info *info);
int psp_assoc_device_get_locked(const struct genl_split_ops *ops,
struct sk_buff *skb, struct genl_info *info);
+int psp_device_get_locked_dev_assoc(const struct genl_split_ops *ops,
+ struct sk_buff *skb,
+ struct genl_info *info);
void
psp_device_unlock(const struct genl_split_ops *ops, struct sk_buff *skb,
struct genl_info *info);
diff --git a/net/psp/psp.h b/net/psp/psp.h
index 0f9c4e4e52cb..c82b21bae240 100644
--- a/net/psp/psp.h
+++ b/net/psp/psp.h
@@ -15,6 +15,7 @@ extern struct mutex psp_devs_lock;

void psp_dev_free(struct psp_dev *psd);
int psp_dev_check_access(struct psp_dev *psd, struct net *net, bool admin);
+int psp_attach_netdev_notifier(void);

void psp_nl_notify_dev(struct psp_dev *psd, u32 cmd);

diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index 792a47105a6c..a57d30db22be 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -391,6 +391,82 @@ int psp_dev_rcv(struct sk_buff *skb, u16 dev_id, u8 generation, bool strip_icv)
}
EXPORT_SYMBOL(psp_dev_rcv);

+static void psp_dev_disassoc_one(struct psp_dev *psd, struct net_device *dev)
+{
+ struct psp_assoc_dev *entry, *tmp;
+
+ list_for_each_entry_safe(entry, tmp, &psd->assoc_dev_list, dev_list) {
+ if (entry->assoc_dev == dev) {
+ list_del(&entry->dev_list);
+ psd->assoc_dev_cnt--;
+ rcu_assign_pointer(entry->assoc_dev->psp_dev, NULL);
+ netdev_put(entry->assoc_dev, &entry->dev_tracker);
+ kfree(entry);
+ return;
+ }
+ }
+}
+
+static int psp_netdev_event(struct notifier_block *nb, unsigned long event,
+ void *ptr)
+{
+ struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+ struct psp_dev *psd;
+
+ if (event != NETDEV_UNREGISTER)
+ return NOTIFY_DONE;
+
+ rcu_read_lock();
+ psd = rcu_dereference(dev->psp_dev);
+ if (psd && psp_dev_tryget(psd)) {
+ rcu_read_unlock();
+ mutex_lock(&psd->lock);
+ psp_dev_disassoc_one(psd, dev);
+ mutex_unlock(&psd->lock);
+ psp_dev_put(psd);
+ } else {
+ rcu_read_unlock();
+ }
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block psp_netdev_notifier = {
+ .notifier_call = psp_netdev_event,
+};
+
+static DEFINE_MUTEX(psp_notifier_lock);
+static bool psp_notifier_registered;
+
+/**
+ * psp_attach_netdev_notifier() - register netdev notifier on first use
+ *
+ * Register the netdevice notifier when the first device association
+ * is created. In many installations no associations will be created and
+ * the notifier won't be needed.
+ *
+ * Must be called without psd->lock held, due to lock ordering:
+ * rtnl_lock -> psd->lock (the notifier callback runs under rtnl_lock
+ * and takes psd->lock).
+ */
+int psp_attach_netdev_notifier(void)
+{
+ int err = 0;
+
+ if (READ_ONCE(psp_notifier_registered))
+ return 0;
+
+ mutex_lock(&psp_notifier_lock);
+ if (!psp_notifier_registered) {
+ err = register_netdevice_notifier(&psp_netdev_notifier);
+ if (!err)
+ WRITE_ONCE(psp_notifier_registered, true);
+ }
+ mutex_unlock(&psp_notifier_lock);
+
+ return err;
+}
+
static int __init psp_init(void)
{
mutex_init(&psp_devs_lock);
diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
index 75ca32821d28..d622f91a979e 100644
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -167,6 +167,22 @@ int psp_device_get_locked(const struct genl_split_ops *ops,
return __psp_device_get_locked(ops, skb, info, false);
}

+/*
+ * Non-admin version of psp_device_get_locked() + psp_attach_netdev_notifier()
+ * only used for dev-assoc.
+ */
+int psp_device_get_locked_dev_assoc(const struct genl_split_ops *ops,
+ struct sk_buff *skb, struct genl_info *info)
+{
+ int err;
+
+ err = psp_attach_netdev_notifier();
+ if (err)
+ return err;
+
+ return __psp_device_get_locked(ops, skb, info, false);
+}
+
static struct net *psp_nl_resolve_assoc_dev_ns(struct psp_dev *psd,
struct genl_info *info)
{
@@ -532,6 +548,19 @@ int psp_nl_dev_assoc_doit(struct sk_buff *skb, struct genl_info *info)
}

psp_assoc_dev->assoc_dev = assoc_dev;
+
+ /* Check for race with NETDEV_UNREGISTER. The cmpxchg above is a
+ * full barrier, and the unregister path has synchronize_net()
+ * between setting NETREG_UNREGISTERING and reading psp_dev in the
+ * notifier. So at least one side would do the clean-up if we are in
+ * the middle of unregitering assoc_dev.
+ * And the clean-up is serialized by psd->lock.
+ */
+ if (READ_ONCE(assoc_dev->reg_state) != NETREG_REGISTERED) {
+ err = -ENODEV;
+ goto rsp_err;
+ }
+
rsp = psp_nl_reply_new(info);
if (!rsp) {
err = -ENOMEM;
--
2.52.0