Pavel Emelyanov wrote: > Oren Laadan wrote: >> 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 :) > > Great! Thanks. > >>>> 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. > > Thank you, Oren and Serge! I will revisit this issue then, but > I have a vacation the next week and, after this, we have a New > Year and Christmas holidays in Russia. So I will be able to go > on with it only after the 7th January :( Hope this is OK for you. > > Besides, Andrew told that he would pay little attention to new > features till the 2.6.24 release, so I'm afraid we won't have this > even in -mm in the nearest months :( Sounds great ! (as for the delay, it wasn't the highest priority issue to begin with, so no worries). Ah.. coincidentally they are celebrated here, too, on the same time :D Merry Christmas and Happy New Year ! Oren. > > Thanks, > Pavel > >> 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
