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

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Message-ID: <20091209091023.GD5129@elte.hu>
Date:	Wed, 9 Dec 2009 10:10:23 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Bryan Donlan <bdonlan@...il.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()


* KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:

> > 
> > * 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).
> 
> Confused.
> 
> I think ptrace don't solve the issue of explained my patch description.

it doesnt. By 'this' i meant the security aspect. ptrace can already do 
almost arbitrary alteration to any task's state.

	Ingo
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