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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 1F0BBC47256 for ; Fri, 1 May 2020 07:48:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08633208C3 for ; Fri, 1 May 2020 07:48:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728420AbgEAHse (ORCPT ); Fri, 1 May 2020 03:48:34 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2139 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728380AbgEAHsd (ORCPT ); Fri, 1 May 2020 03:48:33 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.108]) by Forcepoint Email with ESMTP id 2ACBDF1F7EACDF2BC6BB; Fri, 1 May 2020 08:48:32 +0100 (IST) Received: from [127.0.0.1] (10.47.3.165) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Fri, 1 May 2020 08:48:31 +0100 Subject: Re: [PATCH 13/15] scsi: sas: avoid gcc-10 zero-length-bounds warning To: Arnd Bergmann , , "James E.J. Bottomley" , "Martin K. Petersen" , James Bottomley CC: James Bottomley , Hannes Reinecke , References: <20200430213101.135134-1-arnd@arndb.de> <20200430213101.135134-14-arnd@arndb.de> From: John Garry Message-ID: Date: Fri, 1 May 2020 08:47:49 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20200430213101.135134-14-arnd@arndb.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.3.165] X-ClientProxiedBy: lhreml727-chm.china.huawei.com (10.201.108.78) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 30/04/2020 22:30, Arnd Bergmann wrote: > Two files access the zero-length resp_data[] array, which now > causes a compiler warning: > > drivers/scsi/aic94xx/aic94xx_tmf.c: In function 'asd_get_tmf_resp_tasklet': > drivers/scsi/aic94xx/aic94xx_tmf.c:291:22: warning: array subscript 3 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[0]'} [-Wzero-length-bounds] > 291 | res = ru->resp_data[3]; > | ~~~~~~~~~~~~~^~~ > In file included from include/scsi/libsas.h:15, > from drivers/scsi/aic94xx/aic94xx.h:16, > from drivers/scsi/aic94xx/aic94xx_tmf.c:11: > include/scsi/sas.h:557:9: note: while referencing 'resp_data' > 557 | u8 resp_data[0]; > | ^~~~~~~~~ > drivers/scsi/libsas/sas_task.c: In function 'sas_ssp_task_response': > drivers/scsi/libsas/sas_task.c:21:30: warning: array subscript 3 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[0]'} [-Wzero-length-bounds] > 21 | tstat->stat = iu->resp_data[3]; > | ~~~~~~~~~~~~~^~~ > In file included from include/scsi/scsi_transport_sas.h:8, > from drivers/scsi/libsas/sas_internal.h:14, > from drivers/scsi/libsas/sas_task.c:3: > include/scsi/sas.h:557:9: note: while referencing 'resp_data' > 557 | u8 resp_data[0]; > | ^~~~~~~~~ > > This should really be a flexible-array member, but the structure > already has such a member, swapping it out with sense_data[] would > cause many more warnings elsewhere. > Hi Arnd, If we really prefer flexible-array members over zero-length array members, then could we have a union of flexible-array members? I'm not sure if that's a good idea TBH (or even permitted), as these structures are defined by the SAS spec and good practice to keep as consistent as possible, but just wondering. Apart from that: Reviewed-by: John Garry > As a workaround, add a temporary pointer that can be accessed without > a warning. > > Fixes: 2908d778ab3e ("[SCSI] aic94xx: new driver") > Fixes: 366ca51f30de ("[SCSI] libsas: abstract STP task status into a function") > Signed-off-by: Arnd Bergmann > --- > drivers/scsi/aic94xx/aic94xx_tmf.c | 4 +++- > drivers/scsi/libsas/sas_task.c | 3 ++- > 2 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/aic94xx/aic94xx_tmf.c b/drivers/scsi/aic94xx/aic94xx_tmf.c > index f814026f26fa..a3139f9766c8 100644 > --- a/drivers/scsi/aic94xx/aic94xx_tmf.c > +++ b/drivers/scsi/aic94xx/aic94xx_tmf.c > @@ -269,6 +269,7 @@ static int asd_get_tmf_resp_tasklet(struct asd_ascb *ascb, > struct ssp_frame_hdr *fh; > struct ssp_response_iu *ru; > int res = TMF_RESP_FUNC_FAILED; > + u8 *resp; > > ASD_DPRINTK("tmf resp tasklet\n"); > > @@ -287,8 +288,9 @@ static int asd_get_tmf_resp_tasklet(struct asd_ascb *ascb, > fh = edb->vaddr + 16; > ru = edb->vaddr + 16 + sizeof(*fh); > res = ru->status; > + resp = ru->resp_data; > if (ru->datapres == 1) /* Response data present */ > - res = ru->resp_data[3]; > + res = resp[3]; > #if 0 > ascb->tag = fh->tag; > #endif > diff --git a/drivers/scsi/libsas/sas_task.c b/drivers/scsi/libsas/sas_task.c > index e2d42593ce52..4cd2f9611c4a 100644 > --- a/drivers/scsi/libsas/sas_task.c > +++ b/drivers/scsi/libsas/sas_task.c > @@ -12,13 +12,14 @@ void sas_ssp_task_response(struct device *dev, struct sas_task *task, > struct ssp_response_iu *iu) > { > struct task_status_struct *tstat = &task->task_status; > + u8 *resp = iu->resp_data; > > tstat->resp = SAS_TASK_COMPLETE; > > if (iu->datapres == 0) > tstat->stat = iu->status; > else if (iu->datapres == 1) > - tstat->stat = iu->resp_data[3]; > + tstat->stat = resp[3]; > else if (iu->datapres == 2) { > tstat->stat = SAM_STAT_CHECK_CONDITION; > tstat->buf_valid_size = >