[uml-devel] Re: Patch for buffer overrun in serial/console device logic

[Doug Dumitru <doug@easyco.com>]

Jeff Dike wrote:

> doug@easyco.com said:
> 
>>We also have a much messier, in-house patch that we apply to hostfs.c
>>so  that root mounts will correctly honor ownerships and rights.  
> 
> 
> Does this involve some sort of list on the side which keeps track of ownership
> and permissions of the host files?  If so, hostfs has needed something like
> this for a long time.
> 
> 
>>Is anyone  else working on this.
> 
> 
> Not that I know of.  It comes up every once in a while, but no one has actually
> written any code.
> 
> 				Jeff

The in-house patch that we are running assumes that you boot UML as 
root, although I have considered a SUID root variant.

It looks at numeric UID/GIDs and maintains all of these all the way down 
to the user IO calls.  Thus the files created in the hostfs have 
parellel UID/GID values and priviledges.

The code itself involves a lot of extra parameters from kernel to user 
space as things like the current user aren't propogated down.  I 
personally think that our current patch set is "100% ugly" and would not 
consider posting it as-is.  If people are interested in transparent 
numeric UID/GID to hostfs, then I would be happy to clean up what we 
have and submit it.

Our reason for doing the patch in-house is that we have added UML kernel 
code that supports an in-house application that causes hostfs to keep a 
"journel" of file IO transactions and posts this journel to a host pipe. 
  We then have host daemons (outside of the virtual) that move this 
journel to a distant machine achieving remote filesystem replication. 
We use this for high-reliability mail and web services.

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