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-QBtKwDRP_YJOiOg3=hVvAoEXPc-dG8_SYxQBXHEnjne5wQ@mail.gmail.com>
Date:	Tue, 15 Sep 2015 17:30:56 +0800
From:	Sean Fu <fxinrong@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	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>,
	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 Mon, Sep 14, 2015 at 12:44 AM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> Sean Fu <fxinrong@...il.com> writes:
>
>> On Sat, Sep 12, 2015 at 1:01 AM, Eric W. Biederman
>> <ebiederm@...ssion.com> wrote:
>>> Sean Fu <fxinrong@...il.com> writes:
> '\0' is not and has never been valid in a text file.
> proc files are a text interface.
> Expecting '\0' to be accepted is very strange, and apparently there is
> only one program in existence that does.
>
> That a trailing '\0' was ever accepted was due to a bug in the code.
>
> Accepting '\0' in general in a text interface is a very dangerous and
> buggy pattern so it must be done very carefully or else other
> regressions or bugs could be easily introduced.
Ok,
Could you please give me more detail about the potential risk from the patch?
What is the different behavior between the patch and old kernel?
It seems like entirely same.

> Eric
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