Lin Ma 40acc1aa3e bluetooth: eliminate the potential race condition when removing the HCI controller
commit e2cb6b891a upstream.

There is a possible race condition vulnerability between issuing a HCI
command and removing the cont.  Specifically, functions hci_req_sync()
and hci_dev_do_close() can race each other like below:

thread-A in hci_req_sync()      |   thread-B in hci_dev_do_close()
                                |   hci_req_sync_lock(hdev);
test_bit(HCI_UP, &hdev->flags); |
...                             |   test_and_clear_bit(HCI_UP, &hdev->flags)
hci_req_sync_lock(hdev);        |
                                |
In this commit we alter the sequence in function hci_req_sync(). Hence,
the thread-A cannot issue th.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Cc: Marcel Holtmann <marcel@holtmann.org>
Fixes: 7c6a329e44 ("[Bluetooth] Fix regression from using default link policy")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-05-22 10:57:24 +02:00
2021-04-28 12:08:44 +02:00

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