On Thu, May 14, 2015 at 12:30:45PM -0500, Eric W. Biederman wrote: > > The code is currently available at: > > git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git for-testing > > HEAD: a524faf520600968e58bbc732063fccf2fdf9199 mnt: Update fs_fully_visible to test for permanently empty directories > > The problem: Mounting a new instance of proc of sysfs can allow things > that a bind mount of those filesystems would not. > > That is the cases I am dealing with are: > unshare --user --net --mount ; mount -t sysfs ... > unshare --user --pid --mount ; mount -t proc ... > > The big change is that this set of changes enforces the preservation of > locked mount flags, from the existing mount to the current mount. Which > means that if proc was mounted read-only the current current will allow > a new instance of proc to be mounted read-write, and this set of changes > enforces that proc remain read-only. > > The other gotcha is that the current code does not properly detect empty > directories so to prevent things slipping through the cracks this set of > changes annotates all mount points where nothing will be revealed if > the filesystem mounted on top is removed. > > Enforcing the administrators policy can actually matter in the real > world as has been shown by the recent docker issue. > > With this patchset I have two concerns: > - The enforcement of mount flag preservation on proc and sysfs may break > things. (I am especially worried about the implicit adding of nodev). What do you mean by this? What got added? > - I missed a filesystem mountpoint on proc or sysfs which would make a > fresh copy unmountable for no good reason. > > I don't want to break userspace if I can help it, and the code has been > this way for a while so I figure there is time to find any pitfalls and > address them before this code gets merged. > > So if this works for you please give me your Tested-By > > The well known mountpoints for pseudo filesystems that I could find are: > /dev/ffs*/ functionfs > /dev/gadget/ gadgetfs > /dev/mqueue mqueue > /dev/oprofile/ oprofilefs > /dev/pts/ devpts /dev/shm gets a tmpfs, right? Or do those not matter here? > /dlm/ ocfs2_dlmfs > /ipath/ ipathfs > /proc/fs/nfsd/ nfsd > /proc/openprom/ openpromfs > /proc/sys/fs/binfmt_misc/ binfmt_misc > /spu/ spufs > /sys/firmware/efi/efivars/ efivarfs > /sys/fs/cgroup/ cgroup > /sys/fs/fuse/connections/ fusectl I thought fuse mounted a few more things in here, but I don't know for sure. > /sys/fs/pstore/ pstore > /sys/fs/selinux/ selinuxfs > /sys/fs/smackfs/ smackfs > /sys/hypervisor/s390/ s390_hypfs > /sys/kernel/config/ configfs > /sys/kernel/debug/ debugfs > /sys/kernel/security/ securityfs > /sys/kernel/tracing/ tracefs I think these are all correct for sysfs, I have a minor comment on the sysfs patch I'll make in it. thanks, greg k-h -- 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
