tree 178f244582e959e856fa60f83625112b2df17e88
parent 4a59a3681158a182557c75bacd00d184f9b2a8f5
author Lin Ma <linma@zju.edu.cn> 1637076412 +0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1637923722 +0100

NFC: reorder the logic in nfc_{un,}register_device

[ Upstream commit 3e3b5dfcd16a3e254aab61bd1e8c417dd4503102 ]

There is a potential UAF between the unregistration routine and the NFC
netlink operations.

The race that cause that UAF can be shown as below:

 (FREE)                      |  (USE)
nfcmrvl_nci_unregister_dev   |  nfc_genl_dev_up
  nci_close_device           |
  nci_unregister_device      |    nfc_get_device
    nfc_unregister_device    |    nfc_dev_up
      rfkill_destory         |
      device_del             |      rfkill_blocked
  ...                        |    ...

The root cause for this race is concluded below:
1. The rfkill_blocked (USE) in nfc_dev_up is supposed to be placed after
the device_is_registered check.
2. Since the netlink operations are possible just after the device_add
in nfc_register_device, the nfc_dev_up() can happen anywhere during the
rfkill creation process, which leads to data race.

This patch reorder these actions to permit
1. Once device_del is finished, the nfc_dev_up cannot dereference the
rfkill object.
2. The rfkill_register need to be placed after the device_add of nfc_dev
because the parent device need to be created first. So this patch keeps
the order but inject device_lock to prevent the data race.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Fixes: be055b2f89b5 ("NFC: RFKILL support")
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211116152652.19217-1-linma@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>