On Sun, Jun 09, 2024 at 08:50:24PM GMT, Serge E. Hallyn wrote: > On Sun, Jun 09, 2024 at 03:43:34AM -0700, Jonathan Calmels wrote: > > Attackers often rely on user namespaces to get elevated (yet confined) > > privileges in order to target specific subsystems (e.g. [1]). Distributions > > I'd modify this to say "in order to target *bugs* in specific subsystems" :) Ack > > This effectively mimics the inheritable set rules and means that, by > > default, only root in the user namespace can regain userns capabilities > > previously dropped: > > Something about this last sentence feels wrong, but I'm not sure what > the best alternative would be. As is, though, it makes it sound as though > root in the userns can always regain previously dropped capabilities, but > that's not true if dropped in ancestor ns, or if root also dropped the > bits from its bounding set (right?). Right, the wording is a little bit confusing here I admit. What I meant to say is that if a cap is dropped in a *given* namespace, then it can only be regained by root there. But yes, caps can never be regained from ancestors ns. I'll try to rephrase it. BTW, this is rather strict, but I think that's what we want right, something simple? Alternative would be to have a new cap masked off by default, but if granted to a userns, allows you to regain ancestors caps.
