> > > > On mount propagation, let the owner of the clone be inherited from the > > > > parent into which it has been propagated. Also if the parent has the > > > > "nosuid" flag, set this flag for the child as well. > > > > > > What about nodev? > > > > Hmm, I think the nosuid thing is meant to prevent suid mounts being > > introduced into a "suidless" namespace. This doesn't apply to dev > > mounts, which are quite safe in a suidless environment, as long as the > > user is not able to create devices. But that should be taken care of > > by capability tests. > > > > I'll update the description. > > Hmm, > > Part of me wants to say the safest thing for now would be to refuse > mounts propagation from non-user mounts to user mounts. > > I assume you're thinking about a fully user-mounted chroot, where > the user woudl still want to be able to stick in a cdrom and have > it automounted under /mnt/cdrom, propagated from the root mounts ns? Right. > But then are there no devices which the user could create on a floppy > while inserted into his own laptop, owned by his own uid, then insert > into this machine, and use the device under the auto-mounted /dev/floppy > to gain inappropriate access? I assume, that the floppy and cdrom are already mounted with nosuid,nodev. The problem case is I think is if a sysadmin does some mounting in the initial namespace, and this is propagated into the fully user-mounted namespace (or chroot), so that a mount with suid binaries slips in. Which is bad, because the user may be able rearange the namespace, to trick the suid program to something it should not do. OTOH, a mount with devices can't be abused this way, since it is not possible to gain privileges to files/devices just by rearanging the mounts. Miklos - 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
