From: Andrew Morton <akpm@linux-foundation.org>
To: Trent Piepho <tpiepho@gmail.com>
Cc: linux-kernel@vger.kernel.org, andy@kernel.org, oskar@scara.com,
Daniel Latypov <dlatypov@google.com>,
Yiyuan Guo <yguoaz@gmail.com>
Subject: Re: [PATCH v2 1/2] lib/math/rational.c: Fix divide by zero
Date: Tue, 25 May 2021 14:46:54 -0700 [thread overview]
Message-ID: <20210525144654.e41cb942a2804d08127ad48f@linux-foundation.org> (raw)
In-Reply-To: <20210525144250.214670-1-tpiepho@gmail.com>
On Tue, 25 May 2021 07:42:49 -0700 Trent Piepho <tpiepho@gmail.com> wrote:
> If the input is out of the range of the allowed values, either larger
> than the largest value or closer to zero than the smallest non-zero
> allowed value, then a division by zero would occur.
>
> In the case of input too large, the division by zero will occur on the
> first iteration. The best result (largest allowed value) will be found
> by always choosing the semi-convergent and excluding the denominator
> based limit when finding it.
>
> In the case of the input too small, the division by zero will occur on
> the second iteration. The numerator based semi-convergent should not be
> calculated to avoid the division by zero. But the semi-convergent vs
> previous convergent test is still needed, which effectively chooses
> between 0 (the previous convergent) vs the smallest allowed fraction
> (best semi-convergent) as the result.
Is there any known userspace workload which can trigger this?
IOW, should it be backported into -stable and fast-tracked into 5.13 or
will a 5.14 merge suffice?
next prev parent reply other threads:[~2021-05-25 21:47 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 14:42 Trent Piepho
2021-05-25 14:42 ` [PATCH v2 2/2] lib/math/rational: Add Kunit test cases Trent Piepho
2021-05-25 16:00 ` Andy Shevchenko
2021-05-25 17:34 ` Daniel Latypov
2021-05-25 21:09 ` Trent Piepho
2021-05-25 22:03 ` Daniel Latypov
2021-05-25 21:49 ` Andrew Morton
2021-05-25 16:00 ` [PATCH v2 1/2] lib/math/rational.c: Fix divide by zero Andy Shevchenko
2021-05-25 21:46 ` Andrew Morton [this message]
2021-05-26 8:00 ` Andy Shevchenko
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