linux-kernel - Re: [PATCH 1/2][next] scsi: qla2xxx: Replace one-element array with DECLARE_FLEX

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Date:   Sat, 19 Nov 2022 09:44:02 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        GR-QLogic-Storage-Upstream@...vell.com,
        Nilesh Javali <njavali@...vell.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/2][next] scsi: qla2xxx: Replace one-element array with
 DECLARE_FLEX_ARRAY() helper

Le 19/11/2022 à 00:47, Gustavo A. R. Silva a écrit :
> One-element arrays as fake flex arrays are deprecated and we are moving
> towards adopting C99 flexible-array members, instead. So, replace
> one-element array declaration in struct ct_sns_gpnft_rsp, which is
> ultimately being used inside a union:
> 
> drivers/scsi/qla2xxx/qla_def.h:
> 3240 struct ct_sns_gpnft_pkt {
> 3241         union {
> 3242                 struct ct_sns_req req;
> 3243                 struct ct_sns_gpnft_rsp rsp;
> 3244         } p;
> 3245 };
> 
> Important to mention is that doing a build before/after this patch results
> in no binary differences.

Hi,

even with the:

 >   		rspsz = sizeof(struct ct_sns_gpnft_rsp) +
 > -			((vha->hw->max_fibre_devices - 1) *
 > +			(vha->hw->max_fibre_devices *
 >   			    sizeof(struct ct_sns_gpn_ft_data));

change ?

CJ

> 
> This help us make progress towards globally enabling
> -fstrict-flex-arrays=3 [1].
> 
> Link: https://github.com/KSPP/linux/issues/245
> Link: https://github.com/KSPP/linux/issues/193
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>   drivers/scsi/qla2xxx/qla_def.h | 4 ++--
>   drivers/scsi/qla2xxx/qla_gs.c  | 2 +-
>   2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h
> index a26a373be9da..1eea977ef426 100644
> --- a/drivers/scsi/qla2xxx/qla_def.h
> +++ b/drivers/scsi/qla2xxx/qla_def.h
> @@ -3151,12 +3151,12 @@ struct ct_sns_gpnft_rsp {
>   		uint8_t vendor_unique;
>   	};
>   	/* Assume the largest number of targets for the union */
> -	struct ct_sns_gpn_ft_data {
> +	DECLARE_FLEX_ARRAY(struct ct_sns_gpn_ft_data {
>   		u8 control_byte;
>   		u8 port_id[3];
>   		u32 reserved;
>   		u8 port_name[8];
> -	} entries[1];
> +	}, entries);
>   };
>   
>   /* CT command response */
> diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c
> index 64ab070b8716..69d3bc795f90 100644
> --- a/drivers/scsi/qla2xxx/qla_gs.c
> +++ b/drivers/scsi/qla2xxx/qla_gs.c
> @@ -4073,7 +4073,7 @@ int qla24xx_async_gpnft(scsi_qla_host_t *vha, u8 fc4_type, srb_t *sp)
>   		sp->u.iocb_cmd.u.ctarg.req_size = GPN_FT_REQ_SIZE;
>   
>   		rspsz = sizeof(struct ct_sns_gpnft_rsp) +
> -			((vha->hw->max_fibre_devices - 1) *
> +			(vha->hw->max_fibre_devices *
>   			    sizeof(struct ct_sns_gpn_ft_data));
>   
>   		sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev,