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=-13.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 7059FC38A2A for ; Thu, 7 May 2020 21:58:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43C2E20870 for ; Thu, 7 May 2020 21:58:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cz71TAgu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726797AbgEGV6a (ORCPT ); Thu, 7 May 2020 17:58:30 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:52315 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726437AbgEGV6a (ORCPT ); Thu, 7 May 2020 17:58:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588888708; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=YIdhd/O6VYCCThTyaA6We9R20n/Ae/tFi2XoFVio1ws=; b=cz71TAguzSLFarGW6WObXNFwT+SyzAJhNN4PSTRa/Ifq4te4z+TvXdSLDhL4BNCrsEch4L Ee47yNAGCL6+2N5pSON13KIpeJJpFMtKWzJGB9Z0647NlzHu0WM2FwxUTXW8n1s/nRyrFt XtA2Eit8XN5xOlwT4j+Bd0mkwLTOj8U= 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-352-tmgfVTAMOJGL0jzKrrXf8g-1; Thu, 07 May 2020 17:58:23 -0400 X-MC-Unique: tmgfVTAMOJGL0jzKrrXf8g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7B38718B649E; Thu, 7 May 2020 21:58:22 +0000 (UTC) Received: from madcap2.tricolour.ca (unknown [10.3.128.9]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D00B21001B07; Thu, 7 May 2020 21:58:15 +0000 (UTC) Date: Thu, 7 May 2020 17:58:13 -0400 From: Richard Guy Briggs To: "Gustavo A. R. Silva" Cc: Paul Moore , Eric Paris , linux-audit@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] audit: Replace zero-length array with flexible-array Message-ID: <20200507215812.ksvwcykfged7ye2a@madcap2.tricolour.ca> References: <20200507185041.GA13930@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200507185041.GA13930@embeddedor> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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). Reviewed-by: Richard Guy Briggs > --- > 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 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=-13.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 C8C4EC35280 for ; Thu, 7 May 2020 21:58:48 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7A25C2070B for ; Thu, 7 May 2020 21:58:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RhEsQJ2M" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A25C2070B Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com 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=1588888727; 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=Y3w4H1+ye0W3bYmkxdelCyg4k45ijg+4/GgRvY/qaAw=; b=RhEsQJ2MkC8jvQABpjgQqdl1DjhLTRavDHJZWL3YC3dXecam/ywjeiuwZ63fDgDNKREkU3 67nRqiuhKKituFSoCvqXjhrsuAltfIyAyl/ZleEGVbakNQw2txgzDjd7IDsX7rzczDBUw0 hBEjDsbIeGgdJfLWmHjEfrLZgebapps= 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-336-TlFTTdNyMTeKicviM5XoZg-1; Thu, 07 May 2020 17:58:45 -0400 X-MC-Unique: TlFTTdNyMTeKicviM5XoZg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 07496800687; Thu, 7 May 2020 21:58:42 +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 2C6571000079; Thu, 7 May 2020 21:58:41 +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 80BC01809542; Thu, 7 May 2020 21:58:38 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 047LwM4P027691 for ; Thu, 7 May 2020 17:58:22 -0400 Received: by smtp.corp.redhat.com (Postfix) id 775BF10021B3; Thu, 7 May 2020 21:58:22 +0000 (UTC) Received: from madcap2.tricolour.ca (unknown [10.3.128.9]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D00B21001B07; Thu, 7 May 2020 21:58:15 +0000 (UTC) Date: Thu, 7 May 2020 17:58:13 -0400 From: Richard Guy Briggs To: "Gustavo A. R. Silva" Subject: Re: [PATCH] audit: Replace zero-length array with flexible-array Message-ID: <20200507215812.ksvwcykfged7ye2a@madcap2.tricolour.ca> References: <20200507185041.GA13930@embeddedor> MIME-Version: 1.0 In-Reply-To: <20200507185041.GA13930@embeddedor> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-loop: linux-audit@redhat.com 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 10.5.11.22 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 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 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). Reviewed-by: Richard Guy Briggs > --- > 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