On Thu, Aug 25, 2022 at 01:15:46PM -0500, Eric W. Biederman wrote:
Paul Moore paul@paul-moore.com writes:
On Fri, Aug 19, 2022 at 10:45 AM Serge E. Hallyn serge@hallyn.com wrote:
I am hoping we can come up with "something better" to address people's needs, make everyone happy, and bring forth world peace. Which would stack just fine with what's here for defense in depth.
You may well not be interested in further work, and that's fine. I need to set aside a few days to think on this.
I'm happy to continue the discussion as long as it's constructive; I think we all are. My gut feeling is that Frederick's approach falls closest to the sweet spot of "workable without being overly offensive" (*cough*), but if you've got an additional approach in mind, or an alternative approach that solves the same use case problems, I think we'd all love to hear about it.
I would love to actually hear the problems people are trying to solve so that we can have a sensible conversation about the trade offs.
As best I can tell without more information people want to use the creation of a user namespace as a signal that the code is attempting an exploit.
I don't think that's it at all. I think the problem is that it seems you can pretty reliably get a root shell at some point in the future by creating a user namespace, leaving it open for a bit, and waiting for a new announcement of the latest netfilter or whatever exploit that requires root in a user namespace. Then go back to your userns shell and run the exploit.
So i was hoping we could do something more targeted. Be it splitting off the ability to run code under capable_ns code from uid mapping (to an extent), or maybe some limited-livepatch type of thing where certain parts of code become inaccessible to code in a non-init userns after some sysctl has been toggled, or something cooloer that I've failed to think of.
-serge