linux-kernel - Re: [PATCH v6] Added PR_SET_PROCTITLE

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Message-ID: <20091208065725.GA21340@elte.hu>
Date:	Tue, 8 Dec 2009 07:57:25 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Bryan Donlan <bdonlan@...il.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Timo Sirainen <tss@....fi>,
	WANG Cong <xiyou.wangcong@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v6] Added PR_SET_PROCTITLE_AREA option for prctl()


* Bryan Donlan <bdonlan@...il.com> wrote:

> On Tue, Dec 8, 2009 at 12:38 AM, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > * KOSAKI Motohiro <kosaki.motohiro@...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...

That's exactly the point i made. There's no reason not to offer the API 
i suggested as long as permissions are checked (as usual) - because 
ptrace already allows this (and more).

Thanks,

	Ingo
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