From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752645AbdKVMTf (ORCPT ); Wed, 22 Nov 2017 07:19:35 -0500 Received: from mga06.intel.com ([134.134.136.31]:2911 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752322AbdKVMTd (ORCPT ); Wed, 22 Nov 2017 07:19:33 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,436,1505804400"; d="scan'208";a="4748343" From: "Kirill A. Shutemov" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Michal Hocko , "Kirill A. Shutemov" , stable@vger.kernel.org Subject: [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine Date: Wed, 22 Nov 2017 15:19:21 +0300 Message-Id: <20171122121921.64822-1-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.15.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I've made mistake during converting hugetlb code to 5-level paging: in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset(). Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc() if p4d table is not yet allocated. It only can happen in 5-level paging mode. In 4-level paging mode p4d_offset() always returns pgd, so we are fine. Signed-off-by: Kirill A. Shutemov Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging") Cc: # v4.11+ --- mm/hugetlb.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2d2ff5e8bf2b..94a4c0b63580 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, pte_t *pte = NULL; pgd = pgd_offset(mm, addr); - p4d = p4d_offset(pgd, addr); + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return NULL; pud = pud_alloc(mm, p4d, addr); if (pud) { if (sz == PUD_SIZE) { -- 2.15.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: "Kirill A. Shutemov" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Michal Hocko , "Kirill A. Shutemov" , stable@vger.kernel.org Subject: [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine Date: Wed, 22 Nov 2017 15:19:21 +0300 Message-Id: <20171122121921.64822-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: I've made mistake during converting hugetlb code to 5-level paging: in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset(). Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc() if p4d table is not yet allocated. It only can happen in 5-level paging mode. In 4-level paging mode p4d_offset() always returns pgd, so we are fine. Signed-off-by: Kirill A. Shutemov Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging") Cc: # v4.11+ --- mm/hugetlb.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2d2ff5e8bf2b..94a4c0b63580 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, pte_t *pte = NULL; pgd = pgd_offset(mm, addr); - p4d = p4d_offset(pgd, addr); + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return NULL; pud = pud_alloc(mm, p4d, addr); if (pud) { if (sz == PUD_SIZE) { -- 2.15.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org