Serge E. Hallyn wrote: > Quoting Pavel Emelyanov (xemul@xxxxxxxxxx): >> Oren Laadan wrote: >>> Serge E. Hallyn wrote: >>>> Quoting Oren Laadan (orenl@xxxxxxxxxxxxxxx): >>>>> I hate to bring this again, but what if the admin in the container >>>>> mounts an external file system (eg. nfs, usb, loop mount from a file, >>>>> or via fuse), and that file system already has a device that we would >>>>> like to ban inside that container ? >>>> Miklos' user mount patches enforced that if !capable(CAP_MKNOD), >>>> then mnt->mnt_flags |= MNT_NODEV. So that's no problem. >>> Yes, that works to disallow all device files from a mounted file system. >>> >>> But it's a black and white thing: either they are all banned or allowed; >>> you can't have some devices allowed and others not, depending on type >>> A scenario where this may be useful is, for instance, if we some apps in >>> the container to execute withing a pre-made chroot (sub)tree within that >>> container. >>> >>>> But that's been pulled out of -mm! ? Crap. >>>> >>>>> Since anyway we will have to keep a white- (or black-) list of devices >>>>> that are permitted in a container, and that list may change even change >>>>> per container -- why not enforce the access control at the VFS layer ? >>>>> It's safer in the long run. >>>> By that you mean more along the lines of Pavel's patch than my whitelist >>>> LSM, or you actually mean Tetsuo's filesystem (i assume you don't mean that >>>> by 'vfs layer' :), or something different entirely? >>> :) >>> >>> By 'vfs' I mean at open() time, and not at mount(), or mknod() time. >>> Either yours or Pavel's; I tend to prefer not to use LSM as it may >>> collide with future security modules. >> Oren, AFAIS you've seen my patches for device access controller, right? If you mean this one: http://openvz.org/pipermail/devel/2007-September/007647.html then ack :) >> >> Maybe we can revisit the issue then and try to come to agreement on what >> kind of model and implementation we all want? > > That would be great, Pavel. I do prefer your solution over my LSM, so > if we can get an elegant block device control right in the vfs code that > would be my preference. I concur. So it seems to me that we are all in favor of the model where open() of a device will consult a black/white-list. Also, we are all in favor of a non-LSM implementation, Pavel's code being a good example. Oren. > The only thing that makes me keep wanting to go back to an LSM is the > fact that the code defining the whitelist seems out of place in the vfs. > But I guess that's actually separated into a modular cgroup, with the > actual enforcement built in at the vfs. So that's really the best > solution. > > -serge - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
