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Message-ID: <59A0E237.1070501@huawei.com>
Date: Sat, 26 Aug 2017 10:51:35 +0800
From: zhong jiang <zhongjiang@huawei.com>
MIME-Version: 1.0
Subject: Re: [PATCH] futex: avoid undefined behaviour when shift exponent
 is negative
References: <1498045437-7675-1-git-send-email-zhongjiang@huawei.com> <20170621164036.4findvvz7jj4cvqo@gmail.com> <595331FE.3090700@huawei.com> <alpine.DEB.2.20.1706282353190.1890@nanos> <599FB3C4.6000009@huawei.com> <alpine.DEB.2.20.1708252308500.2124@nanos>
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To: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>, akpm@linux-foundation.org, mingo@redhat.com, minchan@kernel.org, mhocko@suse.com, hpa@zytor.com, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhen Lei <thunder.leizhen@huawei.com>

On 2017/8/26 5:13, Thomas Gleixner wrote:
> On Fri, 25 Aug 2017, zhong jiang wrote:
>> From: zhong jiang <zhongjiang@huawei.com>
>> Date: Fri, 25 Aug 2017 12:05:56 +0800
>> Subject: [PATCH v2] futex: avoid undefined behaviour when shift exponent is
>>  negative
> Please do not send patches without changing the subject line so it's clear
> that there is a new patch.
  ok
>> using a shift value < 0 or > 31 will get crap as a result. because
>> it's just undefined. The issue still disturb me, so I try to fix
>> it again by excluding the especially condition.
> Which is obsolete now as this code is unified accross all architectures and
> the shift issue is addressed in the generic version of it. So all
> architectures get the same fix. See:
>
>  http://git.kernel.org/tip/30d6e0a4190d37740e9447e4e4815f06992dd8c3
  ok , I  miss the above patch.
> And no, we won't add that x86 fix before that unification hits mainline
> because that undefined behaviour is harmless as it only affects the user
> space value of the futex. IOW, the caller gets what it asked for: crap.
  Thank you for clarification.

  Regards
 zhongjiang
> Thanks,
>
> 	tglx
>
>
> .
>
 

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