Re: [PATCH] An attempt to have an unlimitedly extendable sys_clone

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

[snip]

>> +static struct long_clone_arg *get_long_clone_arg(int __user
>> *child_tidptr)
>> +{
>> +	int size;
>> +	struct long_clone_arg *carg;
>> +
>> +	if (get_user(size, child_tidptr))
>> +		return ERR_PTR(-EFAULT);
>> +
>> +	if (size > sizeof(struct long_clone_arg))
>> +		return ERR_PTR(-EINVAL);
> 
> This means that software built against a newer kernel won't work on an
> older one. Surely that's not intended?

It is intended. If I ask an old kernel to clone the mq namespace, but
it doesn't support such, that I'd better like to get an -EINVAL error
rather than be silently held in an old global namespace.

[snip]