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

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Date:   Sat, 19 Nov 2022 01:20:09 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.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 11:10:44PM -0800, Kees Cook wrote:
> 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.)

mmh... yeah; and considering they're already going all the way down to
sp->u.iocb_cmd.u.ctarg.req_size, I think accessing sp->u.iocb_cmd.u.ctarg.rsp
is perfectly fine. :)

I'll respin. Thanks for the feedback!
--
Gustavo

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