From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15FB8C433E1 for ; Tue, 19 May 2020 22:46:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5643207E8 for ; Tue, 19 May 2020 22:46:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589928372; bh=a9pqT8KJ66g+xF2tnOt7wMSRGCEp8vB8fOPKZwpRaVs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=vIt8YQtibgQFKiwj4QxKJtuT2s9Nr5yO/zbcjxgxo1Mn6RgMNgjODvk+IXHbAIrz4 87w/g50OqsAe9j+TpAoMHCHwEvLTB2u5fDgT0MU82OpKsWp+MGMvAn/t/oZNdT54zd k4mVtYAH3yJXsoYHAhR74dB3Luv0DwAFe0gcKjq4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728277AbgESWqM (ORCPT ); Tue, 19 May 2020 18:46:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:49132 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726064AbgESWqM (ORCPT ); Tue, 19 May 2020 18:46:12 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 85816205CB; Tue, 19 May 2020 22:46:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589928371; bh=a9pqT8KJ66g+xF2tnOt7wMSRGCEp8vB8fOPKZwpRaVs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EPG/ZSzfIp2yIfDN90ZfsHWqbGYNwNiCwwVJwXmKzd8ZLcklpx5SQX/YHT08t3zl9 ZZrv1TACOd92zdHPKrFhl4qr4WQF0qLV7HMuqr1rFqORmBSwdaMVCF6taJMwujkUTX q+rSss0/3OaOda+I9cIcvTWl2DDFBpJmXupbzlqM= Date: Tue, 19 May 2020 17:50:58 -0500 From: "Gustavo A. R. Silva" To: "Rafael J. Wysocki" Cc: Robert Moore , Erik Kaneda , "Rafael J. Wysocki" , Len Brown , ACPI Devel Maling List , "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" , Linux Kernel Mailing List , "Gustavo A. R. Silva" , Kees Cook Subject: Re: [PATCH] ACPICA: Replace one-element array and use struct_size() helper Message-ID: <20200519225058.GA14138@embeddedor> References: <20200518222722.GA7791@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 19, 2020 at 12:25:13PM +0200, Rafael J. Wysocki wrote: > On Tue, May 19, 2020 at 12:22 AM Gustavo A. R. Silva > wrote: > > > > The current codebase makes use of one-element arrays in the following > > form: > > > > struct something { > > int length; > > u8 data[1]; > > }; > > > > struct something *instance; > > > > instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); > > instance->length = size; > > memcpy(instance->data, source, size); > > > > but the preferred mechanism to declare variable-length types such as > > these ones is a flexible array member[1][2], introduced in C99: > > > > struct foo { > > int stuff; > > struct boo array[]; > > }; > > > > By making use of the mechanism above, we will get a compiler warning > > in case the flexible array does not occur last in the structure, which > > will help us prevent some kind of undefined behavior bugs from being > > inadvertently introduced[3] to the codebase from now on. > > However, the ACPICA code in the kernel comes from an external project > and changes of this type are generally not applicable to it unless > accepted upstream. Hi Rafael, By _accepted upstream_, in this case, you mean the adoption of the flexible-arrays in the whole codebase, first? If this is the case notice that there are hundreds of these flexible-array conversions in mainline, already: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/?qt=grep&q=flexible-array Is this what you mean? Thanks -- Gustavo > > I'll let Erik and Bob take over. > > > Also, make use of the new struct_size() helper to properly calculate the > > size of struct acpi_pnp_device_id_list. > > > > This issue was found with the help of Coccinellea and, audited and > > fixed _manually_. > > > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > > [2] https://github.com/KSPP/linux/issues/21 > > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > > > > Signed-off-by: Gustavo A. R. Silva > > --- > > drivers/acpi/acpica/utids.c | 4 +--- > > include/acpi/actypes.h | 2 +- > > 2 files changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/acpi/acpica/utids.c b/drivers/acpi/acpica/utids.c > > index 3bb06935a2ad3..c2f819a39424a 100644 > > --- a/drivers/acpi/acpica/utids.c > > +++ b/drivers/acpi/acpica/utids.c > > @@ -262,9 +262,7 @@ acpi_ut_execute_CID(struct acpi_namespace_node *device_node, > > * 2) Size of the CID PNP_DEVICE_ID array + > > * 3) Size of the actual CID strings > > */ > > - cid_list_size = sizeof(struct acpi_pnp_device_id_list) + > > - ((count - 1) * sizeof(struct acpi_pnp_device_id)) + > > - string_area_size; > > + cid_list_size = struct_size(cid_list, ids, count) + string_area_size; > > > > cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size); > > if (!cid_list) { > > diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h > > index 4defed58ea338..c7bcda0ad366a 100644 > > --- a/include/acpi/actypes.h > > +++ b/include/acpi/actypes.h > > @@ -1145,7 +1145,7 @@ struct acpi_pnp_device_id { > > struct acpi_pnp_device_id_list { > > u32 count; /* Number of IDs in Ids array */ > > u32 list_size; /* Size of list, including ID strings */ > > - struct acpi_pnp_device_id ids[1]; /* ID array */ > > + struct acpi_pnp_device_id ids[]; /* ID array */ > > }; > > > > /* > > -- > > 2.26.2 > >