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Commit 6b7339f4 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
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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: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarOleg 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 883a2dfd

mm/memory.c

+13 −7
Original line number Diff line number Diff line
@@ -2670,6 +2670,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 


	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)

		return VM_FAULT_SIGSEGV;
@@ -3099,6 +3103,9 @@ static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma, 
			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;



	pte_unmap(page_table);

	/* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */

	if (!vma->vm_ops->fault)

		return VM_FAULT_SIGBUS;

	if (!(flags & FAULT_FLAG_WRITE))

		return do_read_fault(mm, vma, address, pmd, pgoff, flags,

				orig_pte);
@@ -3244,13 +3251,12 @@ static int handle_pte_fault(struct mm_struct *mm, 
	barrier();

	if (!pte_present(entry)) {

		if (pte_none(entry)) {

			if (vma->vm_ops) {

				if (likely(vma->vm_ops->fault))

					return do_fault(mm, vma, address, pte,

							pmd, flags, entry);

			}

			return do_anonymous_page(mm, vma, address,

						 pte, pmd, flags);

			if (vma->vm_ops)

				return do_fault(mm, vma, address, pte, pmd,

						flags, entry);



			return do_anonymous_page(mm, vma, address, pte, pmd,

					flags);

		}

		return do_swap_page(mm, vma, address,

					pte, pmd, flags, entry);