From: Zi Yan <[email protected]> We need to deposit pre-allocated PTE page table when a PMD migration entry is copied in copy_huge_pmd(). Otherwise, we will leak the pre-allocated page and cause a NULL pointer dereference later in zap_huge_pmd().
The missing counters during PMD migration entry copy process are added as well. The bug report is here: https://lkml.org/lkml/2017/10/29/214 Fixes: 84c3fc4e9c563 ("mm: thp: check pmd migration entry in common path") Reported-by: Fengguang Wu <[email protected]> Signed-off-by: Zi Yan <[email protected]> Cc: Kirill A. Shutemov <[email protected]> --- mm/huge_memory.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 269b5df58543..1981ed697dab 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -941,6 +941,9 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd = pmd_swp_mksoft_dirty(pmd); set_pmd_at(src_mm, addr, src_pmd, pmd); } + add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); + atomic_long_inc(&dst_mm->nr_ptes); + pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; goto out_unlock; -- 2.14.2
