linux-kernel - Re: [PATCH 4.19 84/86] dm integrity: fix integrity recalculation that is improperly skipped

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Message-ID: <20200727233135.GL406581@sasha-vm>
Date:   Mon, 27 Jul 2020 19:31:35 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Mike Snitzer <snitzer@...hat.com>
Subject: Re: [PATCH 4.19 84/86] dm integrity: fix integrity recalculation
 that is improperly skipped

On Mon, Jul 27, 2020 at 10:56:35PM +0200, Pavel Machek wrote:
>Hi!
>
>> From: Mikulas Patocka <mpatocka@...hat.com>
>>
>> commit 5df96f2b9f58a5d2dc1f30fe7de75e197f2c25f2 upstream.
>>
>> Commit adc0daad366b62ca1bce3e2958a40b0b71a8b8b3 ("dm: report suspended
>> device during destroy") broke integrity recalculation.
>>
>> The problem is dm_suspended() returns true not only during suspend,
>> but also during resume. So this race condition could occur:
>> 1. dm_integrity_resume calls queue_work(ic->recalc_wq, &ic->recalc_work)
>> 2. integrity_recalc (&ic->recalc_work) preempts the current thread
>> 3. integrity_recalc calls if (unlikely(dm_suspended(ic->ti))) goto unlock_ret;
>> 4. integrity_recalc exits and no recalculating is done.
>>
>> To fix this race condition, add a function dm_post_suspending that is
>> only true during the postsuspend phase and use it instead of
>> dm_suspended().
>>
>> Signed-off-by: Mikulas Patocka <mpatocka redhat com>
>
>Something is wrong with signoff here...

Heh, and the same thing happened with the stable tag:

	Cc: stable vger kernel org # v4.18+

But given that this is the way the upstream commit looks like we can't
do much here.

-- 
Thanks,
Sasha