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SubjectPossible race in pc87413_wdt.ko

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_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

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