On Tue, Apr 29, 2014 at 5:21 PM, Serge Hallyn <serge.hallyn@xxxxxxxxxx> wrote: > Quoting Andy Lutomirski (luto@xxxxxxxxxxxxxx): >> > It should be a nonissue so long as we make sure that a file owned by a >> > uid outside the scope of the container may not be changed even though >> > fs_owner_uid is set. Otherwise, it's just a matter of chmod +S on say >> > a shell and anyone who can see the fs from the host will be getting a >> > root shell (assuming said file is owned by the host's uid 0). >> >> I feel like that's too fragile. I'd rather add a rule that one of > > yeah I don't wnat to rush something like that. I'd rather stash > the userns of the task which did the mounting and check against > that. Note that would make it worthless unless and until we allowed > mounting from non-init userns, but then we can only claim "our fs > superblock readers suck and therefore containers can't mount an fs" > so long before we start to feel some shame and audit them... > >> these filesystems always acts like it's nosuid unless you're inside a >> user namespace that matches fs_owner_uid. >> >> Maybe even that is too weird. How about setuid, setgid, and fcaps >> only work on mounts that are in mount namespaces that are owned by the >> current user namespace or one of its parents? IOW, a struct mount is >> only trusted if mnt->mnt_ns->user_ns == current user ns or one of its >> parents? >> >> Untrusted mounts would act like they are nosuid,nodev. Someone can >> try to figure out a safe way to relax nodev at some point. Do you like this variant? We could add a way for global root to mount an fs on behalf of a userns. I'd rather this be more explicit than just mounting it in a mount ns owned by the user namespace, though. --Andy _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
