commit 3cab989a upstream.

Calling unlazy_walk() in walk_component() and do_last() when we find
a symlink that needs to be followed doesn't acquire a reference to vfsmount.
That's fine when the symlink is on the same vfsmount as the parent directory
(which is almost always the case), but it's not always true - one _can_
manage to bind a symlink on top of something.  And in such cases we end up
with excessive mntput().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>