pte_present check on hugetlb_entry fix for 3.15?

[Josh Boyer]

Hi Naoya,

I noticed that your
mm-add-pte_present-check-on-existing-hugetlb_entry-callbacks.patch in
Andrew's -mm tree has been queued for a while and has a CC to stable on
it.  Is that something that should get into 3.15?  I know it doesn't
cleanly apply to Linus' current tree because of the patch before it, but
it seems to be a fairly independent fix.

This originally came up in this thread: https://lkml.org/lkml/2014/3/18/784
as a fix for some issues Sasha was hitting with the generic page walker
changes, but you found it was an existing issue.  We now have a CVE
assigned for this:

http://seclists.org/oss-sec/2014/q2/399

So I'm wondering if you think this should fix the issue and if it should
go into 3.15.  A backported version is below.  I poked Linus about this
early today privately (my fault, apologies) and he had some
questions/comments on the code.

josh