There is a race condition between hugepage migration and change_protection(),
where hugetlb_change_protection() doesn't care about migration entries and
wrongly overwrites them. That causes unexpected results like kernel crash.
This patch adds is_hugetlb_entry_(migration|hwpoisoned) check in this
function and skip all such entries.
Signed-off-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Cc: <sta...@vger.kernel.org> # [3.12+]
---
mm/hugetlb.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git mmotm-2014-07-22-15-58.orig/mm/hugetlb.c
mmotm-2014-07-22-15-58/mm/hugetlb.c
index 863f45f63cd5..1da7ca2e2a02 100644
--- mmotm-2014-07-22-15-58.orig/mm/hugetlb.c
+++ mmotm-2014-07-22-15-58/mm/hugetlb.c
@@ -3355,7 +3355,13 @@ unsigned long hugetlb_change_protection(struct
vm_area_struct *vma,
spin_unlock(ptl);
continue;
}
- if (!huge_pte_none(huge_ptep_get(ptep))) {
+ pte = huge_ptep_get(ptep);
+ if (unlikely(is_hugetlb_entry_migration(pte) ||
+ is_hugetlb_entry_hwpoisoned(pte))) {
+ spin_unlock(ptl);
+ continue;
+ }
+ if (!huge_pte_none(pte)) {
pte = huge_ptep_get_and_clear(mm, address, ptep);
pte = pte_mkhuge(huge_pte_modify(pte, newprot));
pte = arch_make_huge_pte(pte, vma, NULL, 0);
--
1.9.3
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