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=-13.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 0EF7BC38A2A for ; Fri, 8 May 2020 12:12:29 +0000 (UTC) Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [205.139.110.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B672620725 for ; Fri, 8 May 2020 12:12:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VHGhR35V" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B672620725 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-audit-bounces@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588939947; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=dvDwD9o46IQZAj7Uq/OGSjy6ffwLcrj1GS4c+hEP/uI=; b=VHGhR35VEjp0utn9HwWF/QkZVK4TBmN4vh/gK8O5kNK/1J2VWqv0OGj8WN1x+FS77S3Yix ET7Yf8KaLhyr2bFixZM5qxvM10mrCF0i1sfDpjuV4148HGfbNnvR1XKdSXyV3CwFUj/px4 dXSrLSiShCcx/BUZYhaIDH8PPBl5ib0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-494-tEt8AaCLN1yOjESKHNANPA-1; Fri, 08 May 2020 08:12:25 -0400 X-MC-Unique: tEt8AaCLN1yOjESKHNANPA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4ED7B1009600; Fri, 8 May 2020 12:12:17 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0C1EC2E18A; Fri, 8 May 2020 12:12:16 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 731301809543; Fri, 8 May 2020 12:12:12 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 047Mjc6a030396 for ; Thu, 7 May 2020 18:45:38 -0400 Received: by smtp.corp.redhat.com (Postfix) id 973AE1182F1; Thu, 7 May 2020 22:45:38 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast05.extmail.prod.ext.rdu2.redhat.com [10.11.55.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 93010115158 for ; Thu, 7 May 2020 22:45:36 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3412A80CDAF for ; Thu, 7 May 2020 22:45:36 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-313-EJ9HUvUmMjyiP81pDH4F3Q-1; Thu, 07 May 2020 18:45:30 -0400 X-MC-Unique: EJ9HUvUmMjyiP81pDH4F3Q-1 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 C274220725; Thu, 7 May 2020 22:45:28 +0000 (UTC) Date: Thu, 7 May 2020 17:49:55 -0500 From: "Gustavo A. R. Silva" To: Richard Guy Briggs Subject: Re: [PATCH] audit: Replace zero-length array with flexible-array Message-ID: <20200507224955.GA22343@embeddedor> References: <20200507185041.GA13930@embeddedor> <20200507215812.ksvwcykfged7ye2a@madcap2.tricolour.ca> MIME-Version: 1.0 In-Reply-To: <20200507215812.ksvwcykfged7ye2a@madcap2.tricolour.ca> User-Agent: Mutt/1.9.4 (2018-02-28) X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-MIME-Autoconverted: from quoted-printable to 8bit by lists01.pubmisc.prod.ext.phx2.redhat.com id 047Mjc6a030396 X-loop: linux-audit@redhat.com X-Mailman-Approved-At: Fri, 08 May 2020 08:12:11 -0400 Cc: linux-audit@redhat.com, linux-kernel@vger.kernel.org X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline On Thu, May 07, 2020 at 05:58:13PM -0400, Richard Guy Briggs wrote: > On 2020-05-07 13:50, Gustavo A. R. Silva wrote: > > The current codebase makes use of the zero-length array language > > extension to the C90 standard, 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. > > > > Also, notice that, dynamic memory allocations won't be affected by > > this change: > > > > "Flexible array members have incomplete type, and so the sizeof operator > > may not be applied. As a quirk of the original implementation of > > zero-length arrays, sizeof evaluates to zero."[1] > > > > sizeof(flexible-array-member) triggers a warning because flexible array > > members have incomplete type[1]. There are some instances of code in > > which the sizeof operator is being incorrectly/erroneously applied to > > zero-length arrays and the result is zero. Such instances may be hiding > > some bugs. So, this work (flexible-array member conversions) will also > > help to get completely rid of those sorts of issues. > > > > This issue was found with the help of Coccinelle. > > > > [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 > > Sounds reasonable to me. There's another in include/uapi/linux/audit.h Hi, I wouldn't advise to make any of these conversions in include/uapi/ [1][2]. > in struct audit_rule_data buf[0]. This alert also helped me fix another > one in a patchset I'm about to post (and will probably cause a merge > conflict but we can figure that out). Awesome. :) > > Reviewed-by: Richard Guy Briggs > Thanks -- Gustavo [1] https://lore.kernel.org/lkml/20200424121553.GE26002@ziepe.ca/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1e6e9d0f4859ec698d55381ea26f4136eff3afe1 > > --- > > include/linux/audit.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/audit.h b/include/linux/audit.h > > index f9ceae57ca8d..2b63aee6e9fa 100644 > > --- a/include/linux/audit.h > > +++ b/include/linux/audit.h > > @@ -19,7 +19,7 @@ > > struct audit_sig_info { > > uid_t uid; > > pid_t pid; > > - char ctx[0]; > > + char ctx[]; > > }; > > > > struct audit_buffer; > > > > > > -- > > Linux-audit mailing list > > Linux-audit@redhat.com > > https://www.redhat.com/mailman/listinfo/linux-audit > > - RGB > > -- > Richard Guy Briggs > Sr. S/W Engineer, Kernel Security, Base Operating Systems > Remote, Ottawa, Red Hat Canada > IRC: rgb, SunRaycer > Voice: +1.647.777.2635, Internal: (81) 32635 > -- Linux-audit mailing list Linux-audit@redhat.com https://www.redhat.com/mailman/listinfo/linux-audit