Re: [uml-devel] hostfs permissions

[Blaisorblade <blaisorblade@yahoo.it>]

On Friday 10 June 2005 07:34, Karl Chen wrote:
> Hi, I'm doing some large-scale security experiments on Debian
> security.  I'm using UML to do the whole thing on a cluster.

> Hostfs seems to make everything owned by root -- even files
> created by non-root users.
So you are running uml as root?

Or you are running UML as non-root but with hostfs as root filesystem? In this 
case you're possibly seeing the result of a trick made to make it work 
well... but I don't know if that trick is present in the UML version you're 
using.

> I'm currently using 2.4.26-3 (Debian 
> package).
Hmm, in that case
> I found a few posts via Google mentioning a patch to 
> fix this, but no other information.  What is the modified behavior
> of hostfs permissions?  Has this been integrated into a newer
> version, or is it in cvs, or if not, are there plans to?
Well, there are:
1) HUMFS, implementing the ideal behaviour below
2) a patch posted by somebody for when UML is run by root, to allow created 
files to get the UID of the process creating it inside UML.

> [I think the ideal behavior, if UML is running as non-root, would
> be if there were a temporary mapping of ownership (e.g. so chown
> works) -- but that would be a lot of work to implement.]
Well, this work has been started but is currently stalled because of other 
ongoing work, however I hope we'll resurrect that shortly.
> I would be happy if there were uid and gid mount options as many
> other fs types have -- to treat all files in the entire mount as
> owned by a particular user/group.

Well, I'm going to add those options to UML 2.6 but I'll be able to work on 
this only next week... However this should not be too much work.
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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