[PATCH net-next v2] net: airoha: Delay offloading until all net_devices are fully registered

[Lorenzo Bianconi]

Netfilter flowtable can theoretically try to offload flower rules as soon
as a net_device is registered while all the other ones are not
registered or initialized, triggering a possible NULL pointer dereferencing
of qdma pointer in airoha_ppe_set_cpu_port routine. Moreover, if
register_netdev() fails for a particular net_device, there is a small
race if Netfilter tries to offload flowtable rules before all the
net_devices are properly unregistered in airoha_probe() error patch,
triggering a NULL pointer dereferencing in airoha_ppe_set_cpu_port
routine. In order to avoid any possible race, delay offloading until
all net_devices are registered in the networking subsystem.

Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
---
Changes in v2:
- Do not grab flow_offload_mutex in airoha_register_gdm_devices() since
  it can trigger a deadlock. Add DEV_STATE_REGISTERED flag instead to
  mark when all net_devices are fully registered.
- Link to v1: https://lore.kernel.org/r/20260324-airoha-regiser-race-fix-v1-1-6014df55886b@kernel.org
---
 drivers/net/ethernet/airoha/airoha_eth.c | 2 ++
 drivers/net/ethernet/airoha/airoha_eth.h | 1 +
 drivers/net/ethernet/airoha/airoha_ppe.c | 7 +++++++
 3 files changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 82e53c60f561f6314fbf201ba8bc8711e40edc68..743ef0db30980ce74059dfb63553030ef3bf735f 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -2957,6 +2957,8 @@ static int airoha_register_gdm_devices(struct airoha_eth *eth)
 			return err;
 	}
 
+	set_bit(DEV_STATE_REGISTERED, &eth->state);
+
 	return 0;
 }
 
diff --git a/drivers/net/ethernet/airoha/airoha_eth.h b/drivers/net/ethernet/airoha/airoha_eth.h
index 7df4dbcd8861856c54c2a38bc89c69180ac2f6dc..af29fc74165b8fffb59f45b4725dbd963f1b876d 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.h
+++ b/drivers/net/ethernet/airoha/airoha_eth.h
@@ -88,6 +88,7 @@ enum {
 
 enum {
 	DEV_STATE_INITIALIZED,
+	DEV_STATE_REGISTERED,
 };
 
 enum {
diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c
index 58b14aea7c2f33ebce11c51d892eefff692378ca..c057bb2d105d92947bb8c421d89ee94fc0c10f2f 100644
--- a/drivers/net/ethernet/airoha/airoha_ppe.c
+++ b/drivers/net/ethernet/airoha/airoha_ppe.c
@@ -1389,6 +1389,13 @@ int airoha_ppe_setup_tc_block_cb(struct airoha_ppe_dev *dev, void *type_data)
 	struct airoha_eth *eth = ppe->eth;
 	int err = 0;
 
+	/* Netfilter flowtable can try to offload flower rules while not all
+	 * the net_devices are registered or initialized. Delay offloading
+	 * until all net_devices are registered in the system.
+	 */
+	if (!test_bit(DEV_STATE_REGISTERED, &eth->state))
+		return -EBUSY;
+
 	mutex_lock(&flow_offload_mutex);
 
 	if (!eth->npu)

---
base-commit: ced629dc8e5c51ff2b5d847adeeb1035cd655d58
change-id: 20260321-airoha-regiser-race-fix-fe854f61d760

Best regards,
-- 
Lorenzo Bianconi <lorenzo at kernel.org>