linux-kernel - Re: [PATCH] posix-timers: fix stack info leak in timer

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Date:	Sun, 5 Oct 2014 23:24:47 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	Mathias Krause <minipli@...glemail.com>,
	linux-kernel@...r.kernel.org,
	Brad Spengler <spender@...ecurity.net>,
	PaX Team <pageexec@...email.hu>
Subject: Re: [PATCH] posix-timers: fix stack info leak in timer_create()

On Sun, 5 Oct 2014, Oleg Nesterov wrote:
> In any case this all looks confusing to me. sys_timer_create() does
> 
> 	new_timer->sigq->info.si_value = event.sigev_value;
> 	new_timer->sigq->info.si_tid   = new_timer->it_id;
> 
> later, this writes to the differents members (_rt and _timer) in the
> same union. But the comment in struct siginfo says that we should use
> _timer. And copy_siginfo_to_user() reports si_tid and si_ptr, this
> again reads _timer and _rt. This should actually work, _sigval should
> have the same offset in both struct's, still it looks confusing imho.

It does.

> Perhaps we should change
> 
> 	#define si_value	_sifields._rt._sigval
> 	#define si_int		_sifields._rt._sigval.sival_int
> 	#define si_ptr		_sifields._rt._sigval.sival_ptr
> 
> to use _timer instead. Nevermind, this is off-topic.

Well that would cause mqueue, perf and procfs to read/set the timer
fields. Odd as well.

Thanks,

	tglx
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