nfc: replace improper check device_is_registered() in netlink related functions
commit da5c0f119203ad9728920456a0f52a6d850c01cd upstream.
The device_is_registered() in nfc core is used to check whether
nfc device is registered in netlink related functions such as
nfc_fw_download(), nfc_dev_up() and so on. Although device_is_registered()
is protected by device_lock, there is still a race condition between
device_del() and device_is_registered(). The root cause is that
kobject_del() in device_del() is not protected by device_lock.
(cleanup task) | (netlink task)
|
nfc_unregister_device | nfc_fw_download
device_del | device_lock
... | if (!device_is_registered)//(1)
kobject_del//(2) | ...
... | device_unlock
The device_is_registered() returns the value of state_in_sysfs and
the state_in_sysfs is set to zero in kobject_del(). If we pass check in
position (1), then set zero in position (2). As a result, the check
in position (1) is useless.
This patch uses bool variable instead of device_is_registered() to judge
whether the nfc device is registered, which is well synchronized.
Fixes: 3e256b8f8dfa ("NFC: add nfc subsystem core")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 file changed