Re: [uml-devel] T-mode processes

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

On Wednesday 06 October 2004 02:00, Henrik Nordstrom wrote:
> On Tue, 5 Oct 2004, BlaisorBlade wrote:
> > Since opening /proc/mm is more or less like creating a new process (or
> > even like forking), dumpable can become 1, following the general Linux
> > rules.
>
> only if it was 1 for the process I think.
These are the general Linux rules applied on fork.
> If it was 0 for the process then 
> there is a obvious risk that sensitive pages will get migrated to the new
> mm.

> creating a new memory map within the process is not really the same as
> exec if I understand SKAS correctly. The two memory maps may be set to
> share a significant portion of pages including data pages, 

> while on exec   
> you are guaranteed the two memory maps are fully separate unless they
> cooperate via mmap or shm which both have access to.

Hmmm - there is no difference between the two situations. We can expect UML 
creating shared mappings, but that is not entirely different from when two 
processes share memory via mmap. In both cases, they share data (even 
sensitive). Or better, since the file is unlinked, it's like when a parent 
and a child share data through mmap()'ing the same file descriptor.

> If there is need to then it may be possible to add an argument indicating
> that the mm should be dumpable even if sanity checks says it should not,
> but I don't see very much need for this.
No will to implement anything like this.
> > However, that's a problem if a process using /proc/mm changes its
> > setting of mm->dumpable (which happens on uid changes and with prctl).
> > Does in that case the uid of the ptraced process change?
>
> In such case the dumpable attribute needs to be cleared on all mm:s of
> that process. There is no easy way telling which memory maps may contain
> restricted pages on such change of the process status.
Yes, this is what I've implemented. I'm sending the patch for this just now 
(separately because it's via patch-scripts).

Bye
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729



-------------------------------------------------------
This SF.net email is sponsored by: IT Product Guide on ITManagersJournal
Use IT products in your business? Tell us what you think of them. Give us
Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more
http://productguide.itmanagersjournal.com/guidepromo.tmpl
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel