Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751641AbbEYN5y (ORCPT ); Mon, 25 May 2015 09:57:54 -0400 Received: from mga01.intel.com ([192.55.52.88]:57786 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751213AbbEYN5x (ORCPT ); Mon, 25 May 2015 09:57:53 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,491,1427785200"; d="scan'208";a="715283000" Date: Mon, 25 May 2015 16:57:41 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jani Nikula Cc: Andrey Ryabinin , David Airlie , Ander Conselvan de Oliveira , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] drm/atomic: fix out of bounds read in for_each_*_in_state helpers Message-ID: <20150525135741.GH18908@intel.com> References: <1432549784-21966-1-git-send-email-a.ryabinin@samsung.com> <87oal8iyxh.fsf@intel.com> <556322E6.3020500@samsung.com> <87lhgcix4s.fsf@intel.com> <87iobgix28.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87iobgix28.fsf@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2523 Lines: 57 On Mon, May 25, 2015 at 04:52:31PM +0300, Jani Nikula wrote: > On Mon, 25 May 2015, Jani Nikula wrote: > > On Mon, 25 May 2015, Andrey Ryabinin wrote: > >> On 05/25/2015 04:12 PM, Jani Nikula wrote: > >>> On Mon, 25 May 2015, Andrey Ryabinin wrote: > >>>> for_each_*_in_state validate array index after > >>>> access to array elements, thus perform out of bounds read. > >>>> > >>>> Fix this by validating index in the first place and read > >>>> array element iff validation was successful. > >>>> > >>>> Fixes: df63b9994eaf ("drm/atomic: Add for_each_{connector,crtc,plane}_in_state helper macros") > >>>> Signed-off-by: Andrey Ryabinin > >>>> --- > >>>> include/drm/drm_atomic.h | 24 ++++++++++++------------ > >>>> 1 file changed, 12 insertions(+), 12 deletions(-) > >>>> > >>>> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h > >>>> index c1571034..3f13b91 100644 > >>>> --- a/include/drm/drm_atomic.h > >>>> +++ b/include/drm/drm_atomic.h > >>>> @@ -77,26 +77,26 @@ int __must_check drm_atomic_async_commit(struct drm_atomic_state *state); > >>>> > >>>> #define for_each_connector_in_state(state, connector, connector_state, __i) \ > >>>> for ((__i) = 0; \ > >>>> - (connector) = (state)->connectors[__i], \ > >>>> - (connector_state) = (state)->connector_states[__i], \ > >>>> - (__i) < (state)->num_connector; \ > >>>> + (__i) < (state)->num_connector && \ > >>>> + ((connector) = (state)->connectors[__i], \ > >>>> + (connector_state) = (state)->connector_states[__i], 1); \ > >>> > >>> This will stop at the first NULL connector/connector_state. Similarly > >>> for the loops below. > >>> > >> > >> This will stop iff (__i) >= (state)->num_connector, because the result of expression: > >> ((connector) = (state)->connectors[__i], (connector_state) = (state)->connector_states[__i], 1) > >> is always 1. > > > > Why do you think it'll always be 1? > > That might be because there's the 1 at the end. *blush*. > > I do wonder if this is too subtle in general, or if it's just too subtle > for me. s/1/true/ might make it a bit less subtle, but not by much. -- Ville Syrj?l? Intel OTC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/