From 395982ce12b3aba14a197ead3e5828e77e11aec1 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 commit d4c54919ed86302094c0ca7d48a8cbd4ee753e92 upstream. 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 Signed-off-by: Andrew Morton [ Backported to 3.15. Signed-off-by: Josh Boyer ] Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/proc/task_mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index fb52b548080d..8f788193e3d4 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1350,7 +1350,7 @@ static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask, struct numa_maps *md; struct page *page; - if (pte_none(*pte)) + if (!pte_present(*pte)) return 0; page = pte_page(*pte); -- cgit v1.2.3