netdev - Re: [PATCH v10 04/20] dlb: add device ioctl layer and first three ioctls

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Message-ID: <YEc/KwOPzvnozaV4@kroah.com>
Date:   Tue, 9 Mar 2021 10:26:03 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mike Ximing Chen <mike.ximing.chen@...el.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        arnd@...db.de, dan.j.williams@...el.com,
        pierre-louis.bossart@...ux.intel.com,
        Gage Eads <gage.eads@...el.com>
Subject: Re: [PATCH v10 04/20] dlb: add device ioctl layer and first three
 ioctls

On Wed, Feb 10, 2021 at 11:54:07AM -0600, Mike Ximing Chen wrote:
> +/*
> + * DLB_CMD_CREATE_SCHED_DOMAIN: Create a DLB 2.0 scheduling domain and reserve
> + *	its hardware resources. This command returns the newly created domain
> + *	ID and a file descriptor for accessing the domain.
> + *
> + * Output parameters:
> + * @response.status: Detailed error code. In certain cases, such as if the
> + *	ioctl request arg is invalid, the driver won't set status.
> + * @response.id: domain ID.
> + * @domain_fd: file descriptor for performing the domain's ioctl operations
> + * @padding0: Reserved for future use.

For all of your paddingX fields, you MUST check that they are set to 0
by userspace now, otherwise they will never be able to actually be used
in the future.

But why do you need them at all anyway?  If something needs to be
changed in the future, just add a new ioctl, don't modify something that
is already working.  Are you _SURE_ you need this type of functionality?

thanks,

greg k-h