Commit 6dc296e7 authored Sep 09, 2015 by Kirill A. Shutemov Committed by Linus Torvalds Sep 10, 2015

mm: make sure all file VMAs have ->vm_ops set



We rely on vma->vm_ops == NULL to detect anonymous VMA: see
vma_is_anonymous(), but some drivers doesn't set ->vm_ops.

As a result we can end up with anonymous page in private file mapping.
That should not lead to serious misbehaviour, but nevertheless is wrong.

Let's fix by setting up dummy ->vm_ops for file mmapping if f_op->mmap()
didn't set its own.

The patch also adds sanity check into __vma_link_rb(). It will help
catch broken VMAs which inserted directly into mm_struct via
insert_vm_struct().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1fcfd8db

mm/mmap.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -612,6 +612,8 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm,
		void __vma_link_rb(struct mm_struct mm, struct vm_area_struct vma,
		struct rb_node *rb_link, struct rb_node rb_parent)
		{
		WARN_ONCE(vma->vm_file && !vma->vm_ops, "missing vma->vm_ops");

		/* Update tracking information for the gap following the new vma. */
		if (vma->vm_next)
		vma_gap_update(vma->vm_next);
		@@ -1636,6 +1638,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
		*/
		WARN_ON_ONCE(addr != vma->vm_start);

		/* All file mapping must have ->vm_ops set */
		if (!vma->vm_ops) {
		static const struct vm_operations_struct dummy_ops = {};
		vma->vm_ops = &dummy_ops;
		}

		addr = vma->vm_start;
		vm_flags = vma->vm_flags;
		} else if (vm_flags & VM_SHARED) {

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