linux-kernel - Re: [PATCH][next] block: scsi_ioctl: Avoid the use of one-element arrays

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Message-ID: <ea92a55b-d12c-357e-62b2-879643ae18ce@kernel.dk>
Date:   Fri, 2 Oct 2020 17:53:05 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH][next] block: scsi_ioctl: Avoid the use of one-element
 arrays

On 10/2/20 5:10 PM, Gustavo A. R. Silva wrote:
> diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h
> index 2817230148fd..6c34f6e2f1f7 100644
> --- a/include/uapi/linux/cdrom.h
> +++ b/include/uapi/linux/cdrom.h
> @@ -289,7 +289,10 @@ struct cdrom_generic_command
>  	unsigned char		data_direction;
>  	int			quiet;
>  	int			timeout;
> -	void			__user *reserved[1];	/* unused, actually */
> +	union {
> +		void		__user *reserved[1];	/* unused, actually */
> +		void            __user *unused;
> +	};

What's the point of this union, why not just turn it into

	void *			__user *unused;

?

-- 
Jens Axboe