We rely on vma->vm_ops == NULL to detect anonymous VMA: see vma_is_anonymous(), but some drivers doesn't set ->vm_ops.
As result we can end up with anonymous page in private file mapping. That's 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 <[email protected]> --- mm/mmap.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index 2e98784d5b7c..a82a02853cbc 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -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) { -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
