Hello,

Please consider including mainline commit
da362b09e42ee0bcaf0356afee6078b4f324baff in the next v3.13.y-ckt
release.  It was
included in the mainline tree as of v3.19-rc1.  It has been tested and
confirmed to resolve http://bugs.launchpad.net/bugs/1541313 .

commit da362b09e42ee0bcaf0356afee6078b4f324baff
Author: Eric W. Biederman [off-list ref]
Date:   Tue Oct 7 12:19:53 2014 -0700

    umount: Do not allow unmounting rootfs.


Sincerely,

Joseph Salisbury