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Message-ID: <b5e6ef12-c2ac-d0ce-b7a1-a58d4c8de300@huawei.com>
Date: Fri, 1 May 2020 08:47:49 +0100
From: John Garry <john.garry@...wei.com>
To: Arnd Bergmann <arnd@...db.de>, <linux-kernel@...r.kernel.org>,
"James E.J. Bottomley" <jejb@...ux.ibm.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
James Bottomley <James.Bottomley@...elEye.com>
CC: James Bottomley <James.Bottomley@...senPartnership.com>,
Hannes Reinecke <hare@...e.com>, <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH 13/15] scsi: sas: avoid gcc-10 zero-length-bounds warning
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 <john.garry@...wei.com>
> 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 <arnd@...db.de>
> ---
> 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 =
>
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