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: <20150825150536.546a73e5@gandalf.local.home>
Date:	Tue, 25 Aug 2015 15:05:36 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
Cc:	Sean Fu <fxinrong@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.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>,
	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, 25 Aug 2015 13:33:57 -0400
Austin S Hemmelgarn <ahferroin7@...il.com> wrote:

> >> How do you know that?
> > I will prove that all other write usage is not impacted later.
> Except that you can only really do this for programs that you have 
> access to, and by definition you can not have access to every program 
> ever written that writes to /proc.
> 
> If you were going to do this, it would need to be itself controlled by 
> another sysctl to toggle the behavior, which would need to default to 
> the current behavior.

Defending the patch, I can't imagine any user space code expecting the
current behavior. The current behavior is that if you write "1\0" it
will error out instead of accepting the "1". I can't come up with a
scenario that would require userspace to expect "1\0" to fail. Can you?


-- Steve
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