Possible race in pc87413_wdt.ko

[Anton Volkov]

Hello.

While searching for races in the Linux kernel I've come across 
"drivers/watchdog/pc87413_wdt.ko" module. Here is a question that I came 
up with while analyzing results. Lines are given using the info from 
Linux v4.12.

Consider the following case:

Thread 1:                          Thread 2:
pc87413_init
   misc_register(&pc87413_miscdev)
-> pc87413_get_swc_base_addr       pc87413_open
                                   -> pc87413_refresh
                                      -> pc87413_swc_bank3
     swc_base_addr = ...                  <read access to swc_base_addr>
     (pc87413_wdt.c: line 133)            (pc87413_wdt.c: line 146)

So in this case preemptive registration of the device leads to a 
possibility of race between the initialization process and a callback to 
the registered device.

Is this race feasible from your point of view? And if it is, is it 
possible to move the device registration a bit further down in the 
pc87413_init function?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: avolkov@xxxxxxxxx