From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752492AbdJ3Oqj (ORCPT ); Mon, 30 Oct 2017 10:46:39 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:35951 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752331AbdJ3Oqh (ORCPT ); Mon, 30 Oct 2017 10:46:37 -0400 X-ME-Sender: From: Zi Yan To: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: "Kirill A . Shutemov" , Zi Yan , Fengguang Wu Subject: [PATCH] mm: migration: deposit page table when copying a PMD migration entry. Date: Mon, 30 Oct 2017 10:46:36 -0400 Message-Id: <20171030144636.4836-1-zi.yan@sent.com> X-Mailer: git-send-email 2.14.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zi Yan 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 Signed-off-by: Zi Yan Cc: Kirill A. Shutemov --- 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