Date: Tue, 8 Dec 2009 06:38:51 +0100
From: Ingo Molnar <mingo@elte.hu>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Bryan Donlan <bdonlan@gmail.com>, Ulrich Drepper <drepper@redhat.com>,
       Timo Sirainen <tss@iki.fi>, WANG Cong <xiyou.wangcong@gmail.com>,
       Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v6] Added PR_SET_PROCTITLE_AREA option for prctl()
Message-ID: <20091208053851.GA12383@elte.hu>
References: <20091208121145.B58D.A69D9226@jp.fujitsu.com>
 <20091208044605.GA32669@elte.hu>
 <20091208135010.B5A8.A69D9226@jp.fujitsu.com>
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* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> > The feature looks useful, but the choice of a prctl as an API is strange 
> > - it limits us to the current task only - while the ability to set 
> > arguments for another task looks a more generic (and potentially more 
> > useful) solution.
> 
> No. It's impossible.
> /proc/{pid}/cmdline read user process's memory. iow, this prctl() don't
> receive string, it receive virtual address itself. [...]

it's not 'impossible' at all, you yourself mention ptrace:

> [...] I don't want any task allow to change another task's memory 
> except ptrace.

And i did not mean to allow 'any' task to be allowed to do this - 
security checks apply, obviously.

	Ingo
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