On Fri, Feb 03, 2023 at 03:50:21PM +0100, D. Starke wrote: > +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? thanks, greg k-h