tree d393b13a5f3f602990157976de26f5526214bf68
parent 72a4346fb1f4128951a8779834ec4a8504da7aea
author Kirill A. Shutemov <kirill.shutemov@linux.intel.com> 1436213917 +0300
committer Adrian Salido <salidoa@google.com> 1479260752 -0800

BACKPORT: mm: avoid setting up anonymous pages into file mapping

(cherry picked from commit 6b7339f4c31ad69c8e9c0b2859276e22cf72176d)

Reading page fault handler code I've noticed that under right
circumstances kernel would map anonymous pages into file mappings: if
the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated
on ->mmap(), kernel would handle page fault to not populated pte with
do_anonymous_page().

Let's change page fault handler to use do_anonymous_page() only on
anonymous VMA (->vm_ops == NULL) and make sure that the VMA is not
shared.

For file mappings without vm_ops->fault() or shred VMA without vm_ops,
page fault on pte_none() entry would lead to SIGBUS.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Willy Tarreau <w@1wt.eu>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: I451f90075ddf0c3592543e4fe30eed4c38348d49
Bug: 32460277