mm: avoid setting up anonymous pages into file mapping

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commit 6b7339f4c3 upstream.

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ luis: backported to 3.16: used Kirill's backport to 3.18 ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

...

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Kirill A. Shutemov 2015-07-06 23:18:37 +03:00 • committed by Luis Henriques

parent 9bc34abfec

commit 9760c0f9a5

1 changed files with 10 additions and 4 deletions

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mm/memory.c

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