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Date:   Mon, 17 Aug 2020 08:07:26 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Qian Cai <cai@lca.pw>
Cc:     Dave Chinner <david@fromorbit.com>,
        Christoph Hellwig <hch@infradead.org>,
        Matthew Wilcox <willy@infradead.org>, darrick.wong@oracle.com,
        linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, khlebnikov@yandex-team.ru
Subject: Re: WARN_ON_ONCE(1) in iomap_dio_actor()
Message-ID: <20200817070726.GA28668@infradead.org>
References: <20200813054418.GB3339@dread.disaster.area>
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On Thu, Aug 13, 2020 at 03:52:13AM -0400, Qian Cai wrote:
> > No sane application would ever do this, it's behaviour as expected,
> > so I don't think there's anything to care about here.
> 
> It looks me the kernel warning is trivial to trigger by an non-root user. Shouldn???t we worry a bit because this could be a DoS for systems which set panic_on_warn?

Yes, we should trigger a WARN_ON on user behavior.  a
pr_info_ratelimited + tracepoint and a good comment is probably the
better solution.