linux-hardening - Re: [PATCH 1/2][next] vfio/ccw: Replace one-element array with flexible-array member

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Date:   Tue, 23 May 2023 19:45:18 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Eric Farman <farman@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/2][next] vfio/ccw: Replace one-element array with
 flexible-array member

Le 23/05/2023 à 03:35, Gustavo A. R. Silva a écrit :
> One-element arrays are deprecated, and we are replacing them with flexible
> array members instead. So, replace one-element array with flexible-array
> member in struct vfio_ccw_parent and refactor the the rest of the code
> accordingly.
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/297
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>   drivers/s390/cio/vfio_ccw_drv.c     | 3 ++-
>   drivers/s390/cio/vfio_ccw_private.h | 2 +-
>   2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
> index ff538a086fc7..57906a9c6324 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -171,7 +171,8 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
>   		return -ENODEV;
>   	}
>   
> -	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> +	parent = kzalloc(sizeof(*parent) + sizeof(struct mdev_type *),

Hi, wouldn't:

    parent = kzalloc(struct_size(parent, mdev_types, 1)),

be more informative and in the spirit of flexible array use?

Just my 2c,

CJ

> +			 GFP_KERNEL);
>   	if (!parent)
>   		return -ENOMEM;
>   
> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
> index b441ae6700fd..b62bbc5c6376 100644
> --- a/drivers/s390/cio/vfio_ccw_private.h
> +++ b/drivers/s390/cio/vfio_ccw_private.h
> @@ -79,7 +79,7 @@ struct vfio_ccw_parent {
>   
>   	struct mdev_parent	parent;
>   	struct mdev_type	mdev_type;
> -	struct mdev_type	*mdev_types[1];
> +	struct mdev_type	*mdev_types[];
>   };
>   
>   /**