linux-kernel - Re: [PATCH] kernel/sysctl.c: If "count" including the terminating byte '\0' the write system call should retrun success.

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Message-ID: <CAGk-QBsNhHH5p4PrG3-sCjKGaUbv1cQ8vAJmdQKVF2iFCbt0+g@mail.gmail.com>
Date:	Tue, 25 Aug 2015 15:50:18 +0800
From:	Sean Fu <fxinrong@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Eric B Munson <emunson@...mai.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Don Zickus <dzickus@...hat.com>,
	Heinrich Schuchardt <xypron.glpk@....de>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/sysctl.c: If "count" including the terminating
 byte '\0' the write system call should retrun success.

On Tue, Aug 25, 2015 at 10:24 AM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>
>
> On August 24, 2015 6:57:57 PM MDT, Sean Fu <fxinrong@...il.com> wrote:
>>An application from HuaWei which works fine on 2.6 encounters this
>>issue on 3.0 or later kernel.
>
> My sympathies.  Being stuck with a 3rd party application you can barely talk about that has been broken for 5years and no one reported it.
>
> Ordinarily we would fix a regression like this. As it has been 5years the challenge now is how do we tell if there are applications that depend on the current behavior.
>
> Before we can change the behavior back we need a convincing argument that we won't cause a regression in another application by making the change.
>
> I do not see how such an argument can be made.  So you have my sympathies but I do not see how we can help you.
We should consider this patch basing on my following arguments.
1 Different version kernel should keep consistent on this behavior.
2 This writting behavior on proc file should be same with writting on
regular file as possible as we can.
3 This patch does not have any potential compatibility risk with 3rd
party application.
4 Support writting "1...\0" to proc file.

>
> Eric
>
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