linux-kernel - Re: WARN_ON_ONCE(1) in iomap_dio

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Message-ID: <20200817070726.GA28668@infradead.org>
Date:   Mon, 17 Aug 2020 08:07:26 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Qian Cai <cai@....pw>
Cc:     Dave Chinner <david@...morbit.com>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>, darrick.wong@...cle.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, khlebnikov@...dex-team.ru
Subject: Re: WARN_ON_ONCE(1) in iomap_dio_actor()

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.