Remove mount points from peer group just before oldroot unmount.

With -K (skip_private_remount) option, there could
be shared mount points under the oldroot.
So, unmounting oldroot triggers unmounting mount
points under the shared mount points, which will be
propagated to the original namespace and corresponding
mount points will be unmounted in those namespaces,
To prevent such unexpected unmounting, this CL remove
mount points being unmounted from peer groups.

Bug: 27689605
TEST=Set up mount points; \
     minijail0 -v -K -b /bin,/bin -P $CONTAINER -- \
         /bin/true; \
     Make sure shared mount points are untouched in \
     the original namespace.

Change-Id: I3dbf7de2a63382c084e4d7e4c2675cc2a6f73c77
1 file changed