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From: Anton Volkov <avolkov@ispras.ru>
To: wim@iguana.be
Cc: linux@roeck-us.net, linux-watchdog@vger.kernel.org,
	linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org,
	Alexey Khoroshilov <khoroshilov@ispras.ru>
Subject: Possible race in pc87413_wdt.ko
Date: Mon, 7 Aug 2017 16:22:17 +0300	[thread overview]
Message-ID: <da42be1b-f442-6294-a163-84e1b971a651@ispras.ru> (raw)

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@ispras.ru

             reply	other threads:[~2017-08-07 13:22 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-07 13:22 Anton Volkov [this message]
2017-08-08  4:10 ` Possible race in pc87413_wdt.ko Guenter Roeck

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