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SubjectRe: kernel stack challenge


Patrick J. LoPresti wrote:

> Whether it is a good idea in this context is another question. My
> concern is that it is hard (impossible?) to bound the memory
> consumption, both stack AND heap, of a Lisp program statically. I
> would expect such bounds to be important for an implementation of a
> security model. With a Lisp program, you cannot be sure under what
> conditions it will exceed whatever space you have alloted for it.
> Which means that, although it cannot crash the kernel, it cannot be
> used to build a reliable system, either...
>

I think 100K is rather large for an interpretor to be included in the
kernel, but putting that aside...

It's a limited number of people who would actually write these policies.
If those people follow certain coding rules, then we CAN have such
bounds, by convention. Yes, those bounds could be violated, but if the
programmer (not sysadmin -- they would never write these things in LISP)
breaks something, it's just a bug.

Mostly it would be kernel programmers who write the policies, and those
would appear in some /etc directory, put there by Red Hat, and
selectable by admins using some GUI.

Someone writing a policy which caused the VM to explode would be no
different from nVidia writing a kernel driver which did it more directly.

The advantage of scripting the policy (which is essentially what this
is) is that they could be switchable more dynamically, and they could
refer to kernel structures more abstractly.

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