Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755398AbcJLNE6 (ORCPT ); Wed, 12 Oct 2016 09:04:58 -0400 Received: from mail.kernel.org ([198.145.29.136]:46588 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754066AbcJLMmK (ORCPT ); Wed, 12 Oct 2016 08:42:10 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Naoya Horiguchi , Hugh Dickins , Dave Hansen , Mel Gorman , Joonsoo Kim , Mike Kravetz , Andrew Morton , Linus Torvalds , Zefan Li Subject: [PATCH 3.4 082/125] mm: hugetlb: call huge_pte_alloc() only if ptep is null Date: Wed, 12 Oct 2016 20:33:18 +0800 Message-Id: <1476275641-4697-82-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1476275600-4626-1-git-send-email-lizf@kernel.org> References: <1476275600-4626-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2321 Lines: 65 From: Naoya Horiguchi 3.4.113-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 0d777df5d8953293be090d9ab5a355db893e8357 upstream. Currently at the beginning of hugetlb_fault(), we call huge_pte_offset() and check whether the obtained *ptep is a migration/hwpoison entry or not. And if not, then we get to call huge_pte_alloc(). This is racy because the *ptep could turn into migration/hwpoison entry after the huge_pte_offset() check. This race results in BUG_ON in huge_pte_alloc(). We don't have to call huge_pte_alloc() when the huge_pte_offset() returns non-NULL, so let's fix this bug with moving the code into else block. Note that the *ptep could turn into a migration/hwpoison entry after this block, but that's not a problem because we have another !pte_present check later (we never go into hugetlb_no_page() in that case.) Fixes: 290408d4a250 ("hugetlb: hugepage migration core") Signed-off-by: Naoya Horiguchi Acked-by: Hillf Danton Acked-by: David Rientjes Cc: Hugh Dickins Cc: Dave Hansen Cc: Mel Gorman Cc: Joonsoo Kim Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [lizf: Backported to 3.4: adjust context] Signed-off-by: Zefan Li --- mm/hugetlb.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index e622aab..416cbfd 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2835,12 +2835,12 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) return VM_FAULT_HWPOISON_LARGE | VM_FAULT_SET_HINDEX(h - hstates); + } else { + ptep = huge_pte_alloc(mm, address, huge_page_size(h)); + if (!ptep) + return VM_FAULT_OOM; } - ptep = huge_pte_alloc(mm, address, huge_page_size(h)); - if (!ptep) - return VM_FAULT_OOM; - /* * Serialize hugepage allocation and instantiation, so that we don't * get spurious allocation failures if two CPUs race to instantiate -- 1.9.1