mm: avoid setting up anonymous pages into file mapping
authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Mon, 6 Jul 2015 20:18:37 +0000 (23:18 +0300)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 9 Jul 2015 18:12:48 +0000 (11:12 -0700)
commit6b7339f4c31ad69c8e9c0b2859276e22cf72176d
treeee208aa15f03b4c7336e56d6767dfecb87be9d7b
parent883a2dfd6f13eca5aab30f0bcc9a6f1e2f983b1e
mm: avoid setting up anonymous pages into file mapping

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>
mm/memory.c