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bluetooth: eliminate the potential race condition when removing the HCI controller

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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>
This commit is contained in:
Lin Ma 2021-04-12 19:17:57 +08:00 committed by Greg Kroah-Hartman
parent 9204ff9486
commit e2cb6b891a
1 changed files with 8 additions and 4 deletions
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12
net/bluetooth/hci_request.c
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@ -272,12 +272,16 @@ int hci_req_sync(struct hci_dev *hdev, int (*req)(struct hci_request *req,
{
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;