linux-kernel - Re: [PATCH AUTOSEL 5.1 35/70] loop: Don't change loop device under exclusive opener

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Message-ID: <20190619201136.GD2226@sasha-vm>
Date:   Wed, 19 Jun 2019 16:11:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        syzbot+10007d66ca02b08f0e60@...kaller.appspotmail.com,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.1 35/70] loop: Don't change loop device under
 exclusive opener

On Mon, Jun 10, 2019 at 11:00:13AM +0200, Jan Kara wrote:
>On Sat 08-06-19 07:39:14, Sasha Levin wrote:
>> From: Jan Kara <jack@...e.cz>
>>
>> [ Upstream commit 33ec3e53e7b1869d7851e59e126bdb0fe0bd1982 ]
>
>Please don't push this to stable kernels because...

I've dropped this, but...

>> [Deliberately chosen not to CC stable as a user with priviledges to
>> trigger this race has other means of taking the system down and this
>> has a potential of breaking some weird userspace setup]
>
>... of this. Thanks!

Can't this be triggered by an "innocent" user, rather as part of an
attack? Why can't this race happen during regular usage?

--
Thanks,
Sasha