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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 25 Feb 2020 13:57:15 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 01PDvDMn42271034 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 25 Feb 2020 13:57:13 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B6BD7A405F; Tue, 25 Feb 2020 13:57:13 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6EDBCA4060; Tue, 25 Feb 2020 13:57:13 +0000 (GMT) Received: from localhost (unknown [9.152.212.204]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 25 Feb 2020 13:57:13 +0000 (GMT) Date: Tue, 25 Feb 2020 14:57:12 +0100 From: Vasily Gorbik To: "Gustavo A. R. Silva" Cc: Heiko Carstens , Christian Borntraeger , Stefan Haberland , Jan Hoeppner , Sebastian Ott , Peter Oberparleiter , Harald Freudenberger , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] s390: Replace zero-length array with flexible-array member References: <20200221150612.GA9717@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200221150612.GA9717@embeddedor> X-TM-AS-GCONF: 00 x-cbid: 20022513-0008-0000-0000-000003564BDD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20022513-0009-0000-0000-00004A7767BB Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-25_04:2020-02-21,2020-02-25 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 bulkscore=0 impostorscore=0 lowpriorityscore=0 adultscore=0 clxscore=1015 suspectscore=0 mlxlogscore=533 phishscore=0 mlxscore=0 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002250109 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 21, 2020 at 09:06:12AM -0600, 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] > > 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 > --- > arch/s390/appldata/appldata_os.c | 2 +- > drivers/s390/block/dasd_diag.c | 2 +- > drivers/s390/block/dasd_eckd.h | 2 +- > drivers/s390/char/raw3270.h | 2 +- > drivers/s390/char/sclp_pci.c | 2 +- > drivers/s390/cio/idset.c | 2 +- > drivers/s390/crypto/pkey_api.c | 2 +- > drivers/s390/crypto/zcrypt_ccamisc.h | 2 +- > drivers/s390/crypto/zcrypt_msgtype6.c | 2 +- > 9 files changed, 9 insertions(+), 9 deletions(-) > Applied, thanks