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 ? 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. Oren. Serge E. Hallyn wrote: > Quoting Tetsuo Handa (penguin-kernel@xxxxxxxxxxxxxxxxxxx): >> Hello. >> >> Serge E. Hallyn wrote: >>> CAP_MKNOD will be removed from its capability >> I think it is not enough because the root can rename/unlink device files >> (mv /dev/sda1 /dev/tmp; mv /dev/sda2 /dev/sda1; mv /dev/tmp /dev/sda2). > > Sure but that doesn't bother us :) > > The admin in the container has his own /dev directory and can do what he > likes with the devices he's allowed to have. He just shouldn't have > access to others. If he wants to rename /dev/sda1 to /dev/sda5 that's > his choice. > >>> To use your approach, i guess we would have to use selinux (or tomoyo) >>> to enforce that devices may only be created under /dev? >> Everyone can use this filesystem alone. > > Sure but it is worthless alone. > > No? > > What will keep the container admin from doing 'mknod /root/hda1 b 3 1'? > >> But use with MAC (or whatever access control mechanisms that prevent >> attackers from unmounting/overlaying this filesystem) is recomennded. > > -serge > _______________________________________________ > Containers mailing list > Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx > https://lists.linux-foundation.org/mailman/listinfo/containers - 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
