linux-kernel - Re: [PATCH 3/3] posix timers: Add syscall that works on timer sigevent

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Message-ID: <20130217134248.GD13378@debjann.fritz.box>
Date:	Sun, 17 Feb 2013 14:42:48 +0100
From:	Jann Horn <jannhorn@...glemail.com>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-api@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] posix timers: Add syscall that works on timer
 sigevent

On Thu, Feb 14, 2013 at 08:19:45PM +0400, Pavel Emelyanov wrote:
> +	struct sigevent event;
[...]
> +	event.sigev_notify = timer->it_sigev_notify;
> +	event.sigev_signo = timer->sigq->info.si_signo;
> +	event.sigev_value = timer->sigq->info.si_value;
> +	event.sigev_notify_thread_id = pid_vnr(timer->it_pid);
[...]
> +	if (old_event && copy_to_user(old_event, &event, sizeof(event)))

Won't this leak uninitialized kernel stack data to userspace? As far as I can
see, the _sigev_un union is bigger than the _tid field in it, so the rest of
it will be copied over without initialization, right?

Jann

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