linux-kernel - RE: [PATCH v3 2/4] tty: n_gsm: add keep alive support

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Date:   Mon, 6 Feb 2023 06:40:51 +0000
From:   "Starke, Daniel" <daniel.starke@...mens.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "ilpo.jarvinen@...ux.intel.com" <ilpo.jarvinen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 2/4] tty: n_gsm: add keep alive support

> > +struct gsm_config_ext {
> > +	__u32 keep_alive;	/* Control channel keep-alive in 1/100th of a
> > +				 * second (0 to disable)
> > +				 */
> > +	__u32 reserved[7];	/* For future use */
> 
> You are not checking these fields, so this means any future use of them
> will not be allowed (like the problem you have which required this new
> structure.)
> 
> Please, always verify that the values here are 0, and if not, error out
> with -EINVAL.  That's the only way you can properly reserve this for
> future use.  The kernel documentation about "how to write an ioctl"
> should describe all of this, right?

gsmld_ioctl() calls for GSMIOC_SETCONF_EXT the function gsm_config_ext()
which returns -EINVAL if any of the reserved fields is non-zero. Should
this also happen for GSMIOC_GETCONF_EXT?

Best regards,
Daniel Starke