[PATCH] An attempt to have an unlimitedly extendable sys_clone

[Dave Hansen]

On Tue, 2008-01-15 at 15:50 +0300, Pavel Emelyanov wrote:
> +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 little bit means that any newer app (with a large
long_clone_arg->size) trying to run on an older kernel (with a smaller
struct) would simply fail to run clone().  Perhaps it shouldn't be _so_
generic as to allow anything in the struct and should stick to bits.
That way, we can actually go look to see whether there are any _unknown_
bits set just like we do now with clone flags.

The more I think about this, the more nervous I get about it.  It is
really neat, but has a bit of the stink of ioctl()s on it.  I'd
personally rather see a new system call.

But, this seems like a good Linus question.  Want to keep us on cc, but
run it by him (and the rest of LKML)?

-- Dave