On Thu, Aug 25, 2022 at 01:15:46PM -0500, Eric W. Biederman wrote: > Paul Moore <paul@xxxxxxxxxxxxxx> writes: > > > On Fri, Aug 19, 2022 at 10:45 AM Serge E. Hallyn <serge@xxxxxxxxxx> 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
