From: Lin Ma linma@zju.edu.cn
commit e2cb6b891ad2b8caa9131e3be70f45243df82a80 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: 7c6a329e4447 ("[Bluetooth] Fix regression from using default link policy") Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bluetooth/hci_request.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/net/bluetooth/hci_request.c +++ b/net/bluetooth/hci_request.c @@ -277,12 +277,16 @@ int hci_req_sync(struct hci_dev *hdev, i { int ret;
- if (!test_bit(HCI_UP, &hdev->flags)) - return -ENETDOWN; - /* Serialize all requests */ hci_req_sync_lock(hdev); - ret = __hci_req_sync(hdev, req, opt, timeout, hci_status); + /* check the state after obtaing the lock to protect the HCI_UP + * against any races from hci_dev_do_close when the controller + * gets removed. + */ + if (test_bit(HCI_UP, &hdev->flags)) + ret = __hci_req_sync(hdev, req, opt, timeout, hci_status); + else + ret = -ENETDOWN; hci_req_sync_unlock(hdev);
return ret;