linux-hardening - Re: [PATCH 2/2][next] scsi: qla2xxx: Use struct_size() in code related to struct ct_sns_gpnft

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Message-ID: <202211182309.D5AC082E3@keescook>
Date:   Fri, 18 Nov 2022 23:10:44 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     "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>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 2/2][next] scsi: qla2xxx: Use struct_size() in code
 related to struct ct_sns_gpnft_rsp

On Fri, Nov 18, 2022 at 05:47:56PM -0600, Gustavo A. R. Silva wrote:
> Prefer struct_size() over open-coded versions of idiom:
> 
> sizeof(struct-with-flex-array) + sizeof(typeof-flex-array-elements) * count
> 
> where count is the max number of items the flexible array is supposed to
> contain.
> 
> Link: https://github.com/KSPP/linux/issues/160
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/scsi/qla2xxx/qla_gs.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c
> index 69d3bc795f90..27e1df56b0fb 100644
> --- a/drivers/scsi/qla2xxx/qla_gs.c
> +++ b/drivers/scsi/qla2xxx/qla_gs.c
> @@ -4072,9 +4072,8 @@ 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 *
> -			    sizeof(struct ct_sns_gpn_ft_data));
> +		rspsz = struct_size((struct ct_sns_gpnft_rsp *)0, entries,
> +				vha->hw->max_fibre_devices);

This should be able to use sp->u.iocb_cmd.u.ctarg.rsp instead of the
explicit struct with a NULL. (It's just using typeof() internally, so
it's okay that it isn't allocated yet.)

-Kees

>  
>  		sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev,
>  								rspsz,
> -- 
> 2.34.1
> 

-- 
Kees Cook