Bluetooth: hci_sync: add lock to protect HCI_UNREGISTER

When the HCI_UNREGISTER flag is set, no jobs should be scheduled. Fix
potential race when HCI_UNREGISTER is set after the flag is tested in
hci_cmd_sync_queue.

Fixes: 0b94f265 ("Bluetooth: hci_sync: Fix queuing commands when HCI_UNREGISTER is set")
Signed-off-by: Zhengping Jiang <jiangzp@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

include/net/bluetooth/hci_core.h

@@ -515,6 +515,7 @@ struct hci_dev {
 	struct work_struct	cmd_sync_work;
 	struct list_head	cmd_sync_work_list;
 	struct mutex		cmd_sync_work_lock;
+	struct mutex		unregister_lock;
 	struct work_struct	cmd_sync_cancel_work;
 	struct work_struct	reenable_adv_work;
 

net/bluetooth/hci_core.c

@@ -2686,7 +2686,9 @@ void hci_unregister_dev(struct hci_dev *hdev)
 {
 	BT_DBG("%p name %s bus %d", hdev, hdev->name, hdev->bus);
 
+	mutex_lock(&hdev->unregister_lock);
 	hci_dev_set_flag(hdev, HCI_UNREGISTER);
+	mutex_unlock(&hdev->unregister_lock);
 
 	write_lock(&hci_dev_list_lock);
 	list_del(&hdev->list);

net/bluetooth/hci_sync.c

@@ -629,6 +629,7 @@ void hci_cmd_sync_init(struct hci_dev *hdev)
 	INIT_WORK(&hdev->cmd_sync_work, hci_cmd_sync_work);
 	INIT_LIST_HEAD(&hdev->cmd_sync_work_list);
 	mutex_init(&hdev->cmd_sync_work_lock);
+	mutex_init(&hdev->unregister_lock);
 
 	INIT_WORK(&hdev->cmd_sync_cancel_work, hci_cmd_sync_cancel_work);
 	INIT_WORK(&hdev->reenable_adv_work, reenable_adv);
@@ -692,14 +693,19 @@ int hci_cmd_sync_submit(struct hci_dev *hdev, hci_cmd_sync_work_func_t func,
 			void *data, hci_cmd_sync_work_destroy_t destroy)
 {
 	struct hci_cmd_sync_work_entry *entry;
+	int err = 0;
 
-	if (hci_dev_test_flag(hdev, HCI_UNREGISTER))
-		return -ENODEV;
+	mutex_lock(&hdev->unregister_lock);
+	if (hci_dev_test_flag(hdev, HCI_UNREGISTER)) {
+		err = -ENODEV;
+		goto unlock;
+	}
 
 	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
-	if (!entry)
-		return -ENOMEM;
-
+	if (!entry) {
+		err = -ENOMEM;
+		goto unlock;
+	}
 	entry->func = func;
 	entry->data = data;
 	entry->destroy = destroy;
@@ -710,7 +716,9 @@ int hci_cmd_sync_submit(struct hci_dev *hdev, hci_cmd_sync_work_func_t func,
 
 	queue_work(hdev->req_workqueue, &hdev->cmd_sync_work);
 
-	return 0;
+unlock:
+	mutex_unlock(&hdev->unregister_lock);
+	return err;
 }
 EXPORT_SYMBOL(hci_cmd_sync_submit);