Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3A66C636CC for ; Mon, 13 Feb 2023 12:52:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231195AbjBMMw5 (ORCPT ); Mon, 13 Feb 2023 07:52:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230412AbjBMMwx (ORCPT ); Mon, 13 Feb 2023 07:52:53 -0500 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 978ABF7; Mon, 13 Feb 2023 04:52:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1676292771; x=1707828771; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=jIAHiOpUZyu4o903XDVaMT723GpUHcMR7GxaRSQTEGg=; b=dZODCAdVPJB2/4xwMShhmyxr/6e+rHdRAh16IzEbHy7FvEUaNKdqgk0w BEWHceepel9sEVMUPIUciWWYFWGOi8MHeFI9E5rI+8HPwciM/Fkp/ZTNm Pi7lwUnljzik8ZlFz3saWFjq2I78+s+JmyeepaLTxNpSwYYj6MCo9ehfy 6eeOhe5+3cyJ72NhQO/m/kJ5J0vdPskVtDznr+DtWxF4S61KIRzRRd8/w OeZanWK0poEgx1BwdqhfMhW3h9F0BFKMTdshOIiILG7shacpjzAsi3vW0 iyWzixWgCDVonTvwO3Qe5HR8mH4P1e/FKRIrj7gkw7/kTXWyGBVx/VIaU Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10619"; a="332190691" X-IronPort-AV: E=Sophos;i="5.97,294,1669104000"; d="scan'208";a="332190691" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Feb 2023 04:52:51 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10619"; a="670809929" X-IronPort-AV: E=Sophos;i="5.97,294,1669104000"; d="scan'208";a="670809929" Received: from aslawinx-mobl.ger.corp.intel.com (HELO [10.99.16.144]) ([10.99.16.144]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Feb 2023 04:52:47 -0800 Message-ID: Date: Mon, 13 Feb 2023 13:52:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.7.2 Subject: Re: [PATCH] ASoC: Intel: Skylake: Replace 1-element array with flex-array To: Kees Cook Cc: Cezary Rojewski , Sasa Ostrouska , Pierre-Louis Bossart , Liam Girdwood , Peter Ujfalusi , Bard Liao , Ranjani Sridharan , Kai Vehmanen , Mark Brown , Takashi Iwai , "Gustavo A. R. Silva" , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org References: <20230210051447.never.204-kees@kernel.org> <54d4ffb1-1488-1a4f-58b2-8b3471389729@linux.intel.com> <63e695c0.620a0220.f69b1.6eec@mx.google.com> Content-Language: en-US From: =?UTF-8?Q?Amadeusz_S=c5=82awi=c5=84ski?= In-Reply-To: <63e695c0.620a0220.f69b1.6eec@mx.google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/10/2023 8:06 PM, Kees Cook wrote: > On Fri, Feb 10, 2023 at 02:10:56PM +0100, Amadeusz Sławiński wrote: >> On 2/10/2023 6:14 AM, Kees Cook wrote: >>> The kernel is globally removing the ambiguous 0-length and 1-element >>> arrays in favor of flexible arrays, so that we can gain both compile-time >>> and run-time array bounds checking[1]. In this instance, struct >>> skl_cpr_cfg contains struct skl_cpr_gtw_cfg, which defined "config_data" >>> as a 1-element array. >>> >>> Normally when switching from a 1-element array to a flex-array, any >>> related size calculations must be adjusted too. However, it seems the >>> original code was over-allocating space, since 1 extra u32 would be >>> included by the sizeof(): >>> >>> param_size = sizeof(struct skl_cpr_cfg); >>> param_size += mconfig->formats_config[SKL_PARAM_INIT].caps_size; >>> >>> But the copy uses caps_size bytes, and cap_size / 4 (i.e. sizeof(u32)) >>> for the length tracking: >>> >>> memcpy(cpr_mconfig->gtw_cfg.config_data, >>> mconfig->formats_config[SKL_PARAM_INIT].caps, >>> mconfig->formats_config[SKL_PARAM_INIT].caps_size); >>> >>> cpr_mconfig->gtw_cfg.config_length = >>> (mconfig->formats_config[SKL_PARAM_INIT].caps_size) / 4; >>> >>> Therefore, no size calculations need adjusting. Change the struct >>> skl_cpr_gtw_cfg config_data member to be a true flexible array, which >>> also fixes the over-allocation, and silences this memcpy run-time false >>> positive: >>> >>> memcpy: detected field-spanning write (size 100) of single field "cpr_mconfig->gtw_cfg.config_data" at sound/soc/intel/skylake/skl-messages.c:554 (size 4) >>> >>> [1] For lots of details, see both: >>> https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays >>> https://people.kernel.org/kees/bounded-flexible-arrays-in-c >>> >>> Reported-by: Sasa Ostrouska >>> Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/ >>> Cc: Cezary Rojewski >>> Cc: Pierre-Louis Bossart >>> Cc: Liam Girdwood >>> Cc: Peter Ujfalusi >>> Cc: Bard Liao >>> Cc: Ranjani Sridharan >>> Cc: Kai Vehmanen >>> Cc: Mark Brown >>> Cc: Jaroslav Kysela >>> Cc: Takashi Iwai >>> Cc: "Gustavo A. R. Silva" >>> Cc: "Amadeusz Sławiński" >>> Cc: alsa-devel@alsa-project.org >>> Signed-off-by: Kees Cook >>> --- >>> sound/soc/intel/skylake/skl-topology.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/sound/soc/intel/skylake/skl-topology.h b/sound/soc/intel/skylake/skl-topology.h >>> index 6db0fd7bad49..ad94f8020c27 100644 >>> --- a/sound/soc/intel/skylake/skl-topology.h >>> +++ b/sound/soc/intel/skylake/skl-topology.h >>> @@ -115,7 +115,7 @@ struct skl_cpr_gtw_cfg { >>> u32 dma_buffer_size; >>> u32 config_length; >>> /* not mandatory; required only for DMIC/I2S */ >>> - u32 config_data[1]; >>> + u32 config_data[]; >>> } __packed; >>> struct skl_dma_control { >> >> This fails in our validation. > > Ah, okay. Thanks for checking! > >> Maybe we can use the union workaround, to >> leave the size as is? >> >> Following seems to work in manual test: >> diff --git a/sound/soc/intel/skylake/skl-topology.h >> b/sound/soc/intel/skylake/skl-topology.h >> index 6db0fd7bad49..ffbd2e60fede 100644 >> --- a/sound/soc/intel/skylake/skl-topology.h >> +++ b/sound/soc/intel/skylake/skl-topology.h >> @@ -115,7 +115,10 @@ struct skl_cpr_gtw_cfg { >> u32 dma_buffer_size; >> u32 config_length; >> /* not mandatory; required only for DMIC/I2S */ >> - u32 config_data[1]; >> + union { >> + u32 x; >> + u32 config_data[0]; >> + }; > > Yeah, that could work, though the last member would be: > DECLARE_FLEX_ARRAY(u32, config_data); > otherwise the array is 0 length (rather than a proper flex array). > > But before that, let me see if I can track down where the size is being > used, in case we can avoid adding the padding. > I did spend some more time on this, apparently struct was missing one field according to IPC protocol. I've send fix for this.