FPII-2702: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>
Change-Id: Ie8aa23d9ced1811eeaf84b2528c4358d84cc4a6f
diff --git a/mm/memory.c b/mm/memory.c
old mode 100644
new mode 100755
index 9ab6e44..720cebe
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3144,6 +3144,10 @@
pte_t entry;
pte_unmap(page_table);
+ /* File mapping without ->vm_ops ? */
+ if (vma->vm_flags & VM_SHARED)
+ return VM_FAULT_SIGBUS;
+
/* Check if we need to add a guard page to the stack */
if (check_stack_guard_page(vma, address) < 0)
@@ -3463,8 +3467,7 @@
if (!pte_present(entry)) {
if (pte_none(entry)) {
if (vma->vm_ops) {
- if (likely(vma->vm_ops->fault))
- return do_linear_fault(mm, vma, address,
+ return do_linear_fault(mm, vma, address,
pte, pmd, flags, entry);
}
return do_anonymous_page(mm, vma, address,