[PATCH] Bluetooth: Fix race between hci_register_dev() and hci_dev_open()

From: Gustavo Padovan <redacted>

If hci_dev_open() is called after hci_register_dev() added the device to
the hci_dev_list but before the workqueue are created we could run into a
NULL pointer dereference (showed in the crash below).

This is bug that is very unlikely to happen, systems using bluetoothd to
manage their bluetooth devices will never see this happens.

BUG: unable to handle kernel NULL pointer dereference
0100
IP: [<ffffffff81077502>] __queue_work+0x32/0x3d0
(...)
Call Trace:
 [<ffffffff81077be5>] queue_work_on+0x45/0x50
 [<ffffffffa016e8ff>] hci_req_run+0xbf/0xf0 [bluetooth]
 [<ffffffffa01709b0>] ? hci_init2_req+0x720/0x720 [bluetooth]
 [<ffffffffa016ea06>] __hci_req_sync+0xd6/0x1c0 [bluetooth]
 [<ffffffff8108ee10>] ? try_to_wake_up+0x2b0/0x2b0
 [<ffffffff8150e3f0>] ? usb_autopm_put_interface+0x30/0x40
 [<ffffffffa016fad5>] hci_dev_open+0x275/0x2e0 [bluetooth]
 [<ffffffffa0182752>] hci_sock_ioctl+0x1f2/0x3f0 [bluetooth]
 [<ffffffff815c6050>] sock_do_ioctl+0x30/0x70
 [<ffffffff815c75f9>] sock_ioctl+0x79/0x2f0
 [<ffffffff811a8046>] do_vfs_ioctl+0x96/0x560
 [<ffffffff811a85a1>] SyS_ioctl+0x91/0xb0
 [<ffffffff816d989d>] system_call_fastpath+0x1a/0x1f

Signed-off-by: Gustavo Padovan <redacted>
---
 net/bluetooth/hci_core.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index dc34bfa..a77d42e 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c

@@ -2165,10 +2165,6 @@ int hci_register_dev(struct hci_dev *hdev)
 
 	BT_DBG("%p name %s bus %d", hdev, hdev->name, hdev->bus);
 
-	write_lock(&hci_dev_list_lock);
-	list_add(&hdev->list, &hci_dev_list);
-	write_unlock(&hci_dev_list_lock);
-
 	hdev->workqueue = alloc_workqueue(hdev->name, WQ_HIGHPRI | WQ_UNBOUND |
 					  WQ_MEM_RECLAIM, 1);
 	if (!hdev->workqueue) {

@@ -2204,6 +2200,10 @@ int hci_register_dev(struct hci_dev *hdev)
 	if (hdev->dev_type != HCI_AMP)
 		set_bit(HCI_AUTO_OFF, &hdev->dev_flags);
 
+	write_lock(&hci_dev_list_lock);
+	list_add(&hdev->list, &hci_dev_list);
+	write_unlock(&hci_dev_list_lock);
+
 	hci_notify(hdev, HCI_DEV_REG);
 	hci_dev_hold(hdev);
 

@@ -2216,9 +2216,6 @@ err_wqueue:
 	destroy_workqueue(hdev->req_workqueue);
 err:
 	ida_simple_remove(&hci_index_ida, hdev->id);
-	write_lock(&hci_dev_list_lock);
-	list_del(&hdev->list);
-	write_unlock(&hci_dev_list_lock);
 
 	return error;
 }

-- 
1.8.1.4