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References: <20091208121145.B58D.A69D9226@jp.fujitsu.com> <20091208044605.GA32669@elte.hu> 
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From: Bryan Donlan <bdonlan@gmail.com>
Date: Tue, 8 Dec 2009 01:28:45 -0500
Message-ID: <3e8340490912072228m70368001v2487bd745ff208b3@mail.gmail.com>
Subject: Re: [PATCH v6] Added PR_SET_PROCTITLE_AREA option for prctl()
To: Ingo Molnar <mingo@elte.hu>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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>
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On Tue, Dec 8, 2009 at 12:38 AM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * 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:

If another process is going to use ptrace to inject the cmdline string
into the victim's address space, it can also temporarily hijack a
thread to run prctl() on its behalf...
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