From d4c54919ed86302094c0ca7d48a8cbd4ee753e92 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Fri, 6 Jun 2014 10:00:01 -0400 Subject: mm: add !pte_present() check on existing hugetlb_entry callbacks The age table walker doesn't check non-present hugetlb entry in common path, so hugetlb_entry() callbacks must check it. The reason for this behavior is that some callers want to handle it in its own way. [ I think that reason is bogus, btw - it should just do what the regular code does, which is to call the "pte_hole()" function for such hugetlb entries - Linus] However, some callers don't check it now, which causes unpredictable result, for example when we have a race between migrating hugepage and reading /proc/pid/numa_maps. This patch fixes it by adding !pte_present checks on buggy callbacks. This bug exists for years and got visible by introducing hugepage migration. ChangeLog v2: - fix if condition (check !pte_present() instead of pte_present()) Reported-by: Sasha Levin Signed-off-by: Naoya Horiguchi Cc: Rik van Riel Cc: [3.12+] Signed-off-by: Andrew Morton [ Backported to 3.15. Signed-off-by: Josh Boyer ] Signed-off-by: Linus Torvalds --- mm/mempolicy.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'mm/mempolicy.c') diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 78e1472..30cc47f8 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -526,9 +526,13 @@ static void queue_pages_hugetlb_pmd_range(struct vm_area_struct *vma, int nid; struct page *page; spinlock_t *ptl; + pte_t entry; ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, (pte_t *)pmd); - page = pte_page(huge_ptep_get((pte_t *)pmd)); + entry = huge_ptep_get((pte_t *)pmd); + if (!pte_present(entry)) + goto unlock; + page = pte_page(entry); nid = page_to_nid(page); if (node_isset(nid, *nodes) == !!(flags & MPOL_MF_INVERT)) goto unlock; -- cgit v1.1