Re: [PATCH] Allow UML kernel to run in a separate host address space

Jeff Dike
2002-12-29T05:00:29Z

torvalds@transmeta.com said:
> But that is an address space that it should already has access to
> through, since it created it in the first place (ie it would fall
> under the normal "sys_mm_indirect()" case).

Yes, and so it doesn't fall under ptrace. I think we're in violent agreement
here.

> The thing that I _really_ don't want to have is soem uncontrolled way
> to generate accesses to existing "struct mm_struct"s, since that is
> really dangerous from a security standpoint.

Fine by me. UML has no need for manipulating pre-existing address spaces.

> We could have a PTRACE_GET_MM_FD kind of thing for ptrace (and then
> the gdb/tracer can use that to create mappings in the process), but
> the reason I want that "hook" to be through ptrace itself is simply
> that it's a known interface to control other unrelated processes.
>
> So if you create the MM's yourself, you can use the indirection
> directly. But if you want to control your children or unrelated
> processes, you use ptrace to get the hook.

Yup. As far as UML is concerned, this is all fine. It has no need of
a PTRACE_GET_MM_FD since it creates all address spaces itself, but other
tools might.

Jeff