linux-kernel - Re: How is Code in do_sys_settimeofday() safe in case of SMP and Nest Kernel Path?

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Message-Id: <200610031203.57328.ak@suse.de>
Date:	Tue, 3 Oct 2006 12:03:57 +0200
From:	Andi Kleen <ak@...e.de>
To:	Pavel Machek <pavel@...e.cz>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Dong Feng <middle.fengdong@...il.com>,
	Christoph Lameter <clameter@....com>,
	Arjan van de Ven <arjan@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	David Howells <dhowells@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: How is Code in do_sys_settimeofday() safe in case of SMP and Nest Kernel Path?

On Tuesday 03 October 2006 10:03, Pavel Machek wrote:
> On Sat 30-09-06 17:03:45, Andi Kleen wrote:
> > 
> > > Did you get to the bottom of this yet? It looks like you're right,
> > > and I suggest a seqlock might be a good option.
> > 
> > It basically doesn't matter because nobody changes the time zone after boot.
> 
> Attacker might; in a tight loop, to confuse time-of-day subsystem, or
> maybe oops the kernel.

(a) only root change it.
(b) the time of day subsystem never cares about the time zone. It is 
just a variable stored for user space.

-Andi
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