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Commit 8937bfa2 authored by Lin Ma's avatar Lin Ma Committed by Greg Kroah-Hartman
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NFC: add NCI_UNREG flag to eliminate the race

commit 48b71a9e

 upstream.

There are two sites that calls queue_work() after the
destroy_workqueue() and lead to possible UAF.

The first site is nci_send_cmd(), which can happen after the
nci_close_device as below

nfcmrvl_nci_unregister_dev   |  nfc_genl_dev_up
  nci_close_device           |
    flush_workqueue          |
    del_timer_sync           |
  nci_unregister_device      |    nfc_get_device
    destroy_workqueue        |    nfc_dev_up
    nfc_unregister_device    |      nci_dev_up
      device_del             |        nci_open_device
                             |          __nci_request
                             |            nci_send_cmd
                             |              queue_work !!!

Another site is nci_cmd_timer, awaked by the nci_cmd_work from the
nci_send_cmd.

  ...                        |  ...
  nci_unregister_device      |  queue_work
    destroy_workqueue        |
    nfc_unregister_device    |  ...
      device_del             |  nci_cmd_work
                             |  mod_timer
                             |  ...
                             |  nci_cmd_timer
                             |    queue_work !!!

For the above two UAF, the root cause is that the nfc_dev_up can race
between the nci_unregister_device routine. Therefore, this patch
introduce NCI_UNREG flag to easily eliminate the possible race. In
addition, the mutex_lock in nci_close_device can act as a barrier.

Signed-off-by: default avatarLin Ma <linma@zju.edu.cn>
Fixes: 6a2968aa

 ("NFC: basic NCI protocol implementation")
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Reviewed-by: default avatarKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211116152732.19238-1-linma@zju.edu.cn


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 99d348b8
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