Re: [uml-devel] RE: uml_switch security fixing

[Blaisorblade <blaisorblade@yahoo.it>]

On Monday 07 March 2005 05:42, Steve Schmidtke wrote:
> Blaisorblade wrote:
> >Hey, has anyone found the time to put together any patch to workaround the
> >security bug in uml_net?

> Attached are two patches.  The first one, uml_net-slip.diff, is the minimal
> patch to apply to uml_net.  The second one, uml_net-uml.diff, applies to
> 2.4.27-1um
Thanks for your time and work!
> (note the half-hearted attempt to plug a FD leak in there as 
> well).
Verified, both seem correct (the closed fd's are local var, so there is no 
possibility they were closed elsewhere).

half-hearted... ok, found in my dictionary!!! Wow!
> As a nice bonus, a UML with this patch still works with an 
> unpatched uml_net binary.
Hmm, this means many users could avoid upgrading... Well, it's their box 
anyway.

But an unpatched UML won't work with a newer uml_net binary (for SLIP usage 
only and only for closing the interface, I mean), right?

I see that this way it's not possible to avoid this (and frankly, I was ready 
to discard SLIP support until the fix was ready, so it is ok). Also the patch 
is very little (and applies unchanged to 2.6.11, so I guess there will be 0 
backporting problems).

I'm applying this nevertheless in my tools (I think I'll forward all this to 
Jeff, or maybe I'll send him a released tarball + the splitout changes), and 
I'm also going to publish as much information as I can (which means 
pre-adding an entry to the Wiki).

I also looked at the versioning for uml_net, but what happens is that we can 
only stop unpatched uml_net from working with newer UML for any protocol, not 
anything else. So I won't change that. However, I just saw that we did it 
correctly until Version 3 of the uml_net protocol...
I wonder what has happened after.

> >I think it would be ok also to simply comment out the offending code (even
> >providing some kind of -D configuration option for who really needs SLIP
> >support, and they are few)!
> >
> >Suggestions?
>
> Agreed, tuntap is a compile time option, slip should be as well.
Ok... tuntap is compile-time because of a rough check for host support.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade





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