[PATCH] Bluetooth: hci_core: Fix race condition during device registration

["syzbot" <syzbot@kernel.org>]

From: Aleksandr Nogikh <nogikh@google.com>

In hci_register_dev(), the power_on work item is queued to
hdev->req_workqueue before initializing hdev->adv_monitors_idr and
registering the MSFT extension via msft_register(). For devices marked with
quirks such as HCI_QUIRK_RAW_DEVICE, the HCI_UNCONFIGURED flag is set on
the device. When the power_on work item runs concurrently on another CPU,
hci_power_on() detects that the device is unconfigured and immediately
invokes hci_dev_do_close(), which calls msft_do_close().

Concurrently, msft_register() allocates the msft structure and exposes it
to hdev->msft_data prior to calling mutex_init(&msft->filter_lock). If
msft_do_close() executes while hdev->msft_data is already assigned but the
mutex has not yet been initialized, mutex_lock(&msft->filter_lock) operates
on an uninitialized mutex, triggering a DEBUG_LOCKS warning:

DEBUG_LOCKS_WARN_ON(lock->magic != lock)
WARNING: kernel/locking/mutex.c:625 at __mutex_lock_common
kernel/locking/mutex.c:625 [inline]
WARNING: kernel/locking/mutex.c:625 at __mutex_lock+0x12d8/0x1550
kernel/locking/mutex.c:821
...
Call Trace:
 <TASK>
 msft_do_close+0x308/0x7b0 net/bluetooth/msft.c:693
 hci_dev_close_sync+0x86b/0x10a0 net/bluetooth/hci_sync.c:5522
 hci_dev_do_close net/bluetooth/hci_core.c:499 [inline]
 hci_power_on+0x32c/0x750 net/bluetooth/hci_core.c:937
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
 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
 </TASK>

Fix this by moving the queue_work() call in hci_register_dev() to after
idr_init(&hdev->adv_monitors_idr) and msft_register(hdev) so that device
structures and extensions are fully initialized before asynchronous tasks
can access them. Additionally, assign hdev->msft_data in msft_register()
only after mutex_init(&msft->filter_lock) has completed.

Fixes: 9e14606d8f38 ("Bluetooth: msft: Extended monitor tracking by address filter")
Assisted-by: Gemini:gemini-3.7-flash Gemini:gemini-3.1-pro-preview syzbot
Reported-by: syzbot+14ce1b05b7d5a989abbe@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=14ce1b05b7d5a989abbe
Link: https://syzkaller.appspot.com/ai_job?id=2bc9e8aa-ca6d-43e2-be2c-fd5d9f649d7e
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>

---
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 5ba9fe826..771b73c99 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -2629,11 +2629,11 @@ int hci_register_dev(struct hci_dev *hdev)
 	if (error)
 		BT_WARN("register suspend notifier failed error:%d\n", error);
 
-	queue_work(hdev->req_workqueue, &hdev->power_on);
-
 	idr_init(&hdev->adv_monitors_idr);
 	msft_register(hdev);
 
+	queue_work(hdev->req_workqueue, &hdev->power_on);
+
 	return id;
 
 err_wqueue:
diff --git a/net/bluetooth/msft.c b/net/bluetooth/msft.c
index d7badce87..255163033 100644
--- a/net/bluetooth/msft.c
+++ b/net/bluetooth/msft.c
@@ -764,8 +764,8 @@ void msft_register(struct hci_dev *hdev)
 
 	INIT_LIST_HEAD(&msft->handle_map);
 	INIT_LIST_HEAD(&msft->address_filters);
-	hdev->msft_data = msft;
 	mutex_init(&msft->filter_lock);
+	hdev->msft_data = msft;
 }
 
 void msft_release(struct hci_dev *hdev)


base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
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