Quoting Eric W. Biederman (ebiederm at xmission.com): > "Serge E. Hallyn" <serue at us.ibm.com> writes: > > > From: Serge E. Hallyn <serue at us.ibm.com> > > Subject: [PATCH 4/8] user ns: hook permission > > > > Hook permission to check vfsmnt->user_ns against current. > > This looks wrong on several levels. > - This should ultimately be inside generic_permission instead of > permission as there are some distributed filesystems that know how to cope with > multiple mount namespaces simultaneous. > > - As implemented the test is not what I would expect. I would > expect comparisons of uid X == uid Y and gid X == gid Y to > be replaced by comparing the tuples of uid namesspace and uid. > Which would allow access to world readable/writeable files, > and it would allow users with CAP_DAC_OVERRIDE to be able to access > everything. Whoa - why on earth would we want that? > All we are really saying as I understand a user namespace is that > instead of uid's uniquely identifying a user the pair the pair uidns, > uid is uniquely identifies a user. Ok that would be one way to interpret it, but it is insufficient for preventing root in one vserver from messing with users in another vserver. > Because you didn't pick what I would consider the obvious choice > you now need an extra mount flag to disable the uid namespace all > together, so you can transition through the intermediate uid namespace > state. That really feels wrong. Some bit of required bootstrapping seems both acceptable and expected to me. > All mounts should have an associated uid namespace and the only check > way you should be able to ignore that is to access filesystems > that can cope with multiple uid namespaces simultaneously. But it's my fs on my box, why shouldn't i be able to say all uid namespaces can acces this subtree read-only, just bc you feel the fs is inadequate? :) Note that the tiniest of trees, with just a statically compiled bash, mount, pivot_mount, and initrc, should suffice, mounted readonly for all uid namespaces to use to bootstrap. -serge