[bug report] hugetlb, mempolicy: fix the mbind hugetlb migration

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Michal Hocko,

This is a semi-automatic email about new static checker warnings.

The patch ef2fc869a863: "hugetlb, mempolicy: fix the mbind hugetlb 
migration" from Jan 5, 2018, leads to the following Smatch complaint:

    mm/mempolicy.c:1100 new_page()
    error: we previously assumed 'vma' could be null (see line 1092)

mm/mempolicy.c
  1091		vma = find_vma(current->mm, start);
  1092		while (vma) {
                       ^^^
There is a check for NULL here

  1093			address = page_address_in_vma(page, vma);
  1094			if (address != -EFAULT)
  1095				break;
  1096			vma = vma->vm_next;
  1097		}
  1098	
  1099		if (PageHuge(page)) {
  1100			return alloc_huge_page_vma(vma, address);
                                                   ^^^
The patch adds a new unchecked dereference.  It might be OK?  I don't
know.

  1101		} else if (PageTransHuge(page)) {
  1102			struct page *thp;

regards,
dan carpenter

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