From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kenneth Graunke <kenneth@whitecape.org>
Subject: Re: [PATCH 22/43] drm/i915: prevent division by zero
 when asking for chipset power
Date: Wed, 14 Dec 2011 11:05:31 -0800
Message-ID: <4EE8F37B.5090709@whitecape.org>
References: <1323867460-5486-1-git-send-email-daniel.vetter@ffwll.ch>
	<1323867460-5486-22-git-send-email-daniel.vetter@ffwll.ch>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org>
Received: from homiemail-a61.g.dreamhost.com (caiajhbdccah.dreamhost.com
	[208.97.132.207])
	by gabe.freedesktop.org (Postfix) with ESMTP id 464119E97A
	for <intel-gfx@lists.freedesktop.org>;
	Wed, 14 Dec 2011 11:03:55 -0800 (PST)
In-Reply-To: <1323867460-5486-22-git-send-email-daniel.vetter@ffwll.ch>
List-Unsubscribe: <http://lists.freedesktop.org/mailman/options/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=unsubscribe>
List-Archive: <http://lists.freedesktop.org/archives/intel-gfx>
List-Post: <mailto:intel-gfx@lists.freedesktop.org>
List-Help: <mailto:intel-gfx-request@lists.freedesktop.org?subject=help>
List-Subscribe: <http://lists.freedesktop.org/mailman/listinfo/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=subscribe>
Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>, Eugeni Dodonov <eugeni.dodonov@intel.com>
List-Id: intel-gfx@lists.freedesktop.org

On 12/14/2011 04:57 AM, Daniel Vetter wrote:
> From: Eugeni Dodonov <eugeni.dodonov@intel.com>
> 
> This prevents an in-kernel division by zero which happens when we are
> asking for i915_chipset_val too quickly, or within a race condition
> between the power monitoring thread and userspace accesses via debugfs.
> 
> The issue can be reproduced easily via the following command:
> while ``; do cat /sys/kernel/debug/dri/0/i915_emon_status; done
> 
> This is particularly dangerous because it can be triggered by
> a non-privileged user by just reading the debugfs entry.
> 
> This issue was also found independently by Konstantin Belousov
> <kostikbel@gmail.com>, who proposed a similar patch.
> 
> Reported-by: Konstantin Belousov <kostikbel@gmail.com>
> Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> Acked-by: Keith Packard <keithp@keithp.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_dma.c |   10 ++++++++++
>  drivers/gpu/drm/i915/i915_drv.h |    1 +
>  2 files changed, 11 insertions(+), 0 deletions(-)

This has been in drm-intel-fixes since December 8th.