From nobody Mon Apr 6 23:08:20 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C079CECAAD3 for ; Thu, 1 Sep 2022 10:42:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233577AbiIAKmY (ORCPT ); Thu, 1 Sep 2022 06:42:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234377AbiIAKlo (ORCPT ); Thu, 1 Sep 2022 06:41:44 -0400 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DCBA012FDE4 for ; Thu, 1 Sep 2022 03:41:40 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VO.fSTD_1662028897; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VO.fSTD_1662028897) by smtp.aliyun-inc.com; Thu, 01 Sep 2022 18:41:38 +0800 From: Baolin Wang To: akpm@linux-foundation.org, mike.kravetz@oracle.com Cc: songmuchun@bytedance.com, david@redhat.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page Date: Thu, 1 Sep 2022 18:41:31 +0800 Message-Id: <635f43bdd85ac2615a58405da82b4d33c6e5eb05.1662017562.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" On some architectures (like ARM64), it can support CONT-PTE/PMD size hugetlb, which means it can support not only PMD/PUD size hugetlb (2M and 1G), but also CONT-PTE/PMD size(64K and 32M) if a 4K page size specified. So when looking up a CONT-PTE size hugetlb page by follow_page(), it will use pte_offset_map_lock() to get the pte entry lock for the CONT-PTE size hugetlb in follow_page_pte(). However this pte entry lock is incorrect for the CONT-PTE size hugetlb, since we should use huge_pte_lock() to get the correct lock, which is mm->page_table_lock. That means the pte entry of the CONT-PTE size hugetlb under current pte lock is unstable in follow_page_pte(), we can continue to migrate or poison the pte entry of the CONT-PTE size hugetlb, which can cause some potential race issues, even though they are under the 'pte lock'. For example, suppose thread A is trying to look up a CONT-PTE size hugetlb page by move_pages() syscall under the lock, however antoher thread B can migrate the CONT-PTE hugetlb page at the same time, which will cause thread A to get an incorrect page, if thread A also wants to do page migration, then data inconsistency error occurs. Moreover we have the same issue for CONT-PMD size hugetlb in follow_huge_pmd(). To fix above issues, rename the follow_huge_pmd() as follow_huge_pmd_pte() to handle PMD and PTE level size hugetlb, which uses huge_pte_lock() to get the correct pte entry lock to make the pte entry stable. Cc: Suggested-by: Mike Kravetz Signed-off-by: Baolin Wang Reviewed-by: Mike Kravetz --- Changes from v2: - Combine PMD and PTE level hugetlb handling into one function. - Drop unnecessary patches. - Update the commit message. Mike, please fold this patch into your series. Thanks. --- include/linux/hugetlb.h | 8 ++++---- mm/gup.c | 14 +++++++++++++- mm/hugetlb.c | 27 +++++++++++++-------------- 3 files changed, 30 insertions(+), 19 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 852f911..fe4944f 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -207,8 +207,8 @@ struct page *follow_huge_addr(struct mm_struct *mm, uns= igned long address, struct page *follow_huge_pd(struct vm_area_struct *vma, unsigned long address, hugepd_t hpd, int flags, int pdshift); -struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, - pmd_t *pmd, int flags); +struct page *follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long= address, + int flags); struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address, pud_t *pud, int flags); struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address, @@ -319,8 +319,8 @@ static inline struct page *follow_huge_pd(struct vm_are= a_struct *vma, return NULL; } =20 -static inline struct page *follow_huge_pmd(struct mm_struct *mm, - unsigned long address, pmd_t *pmd, int flags) +static inline struct page *follow_huge_pmd_pte(struct vm_area_struct *vma, + unsigned long address, int flags) { return NULL; } diff --git a/mm/gup.c b/mm/gup.c index 66d8619e..1e74fc0 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -530,6 +530,18 @@ static struct page *follow_page_pte(struct vm_area_str= uct *vma, if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) =3D=3D (FOLL_PIN | FOLL_GET))) return ERR_PTR(-EINVAL); + + /* + * Considering PTE level hugetlb, like continuous-PTE hugetlb on + * ARM64 architecture. + */ + if (is_vm_hugetlb_page(vma)) { + page =3D follow_huge_pmd_pte(vma, address, flags); + if (page) + return page; + return no_page_table(vma, flags); + } + retry: if (unlikely(pmd_bad(*pmd))) return no_page_table(vma, flags); @@ -662,7 +674,7 @@ static struct page *follow_pmd_mask(struct vm_area_stru= ct *vma, if (pmd_none(pmdval)) return no_page_table(vma, flags); if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) { - page =3D follow_huge_pmd(mm, address, pmd, flags); + page =3D follow_huge_pmd_pte(vma, address, flags); if (page) return page; return no_page_table(vma, flags); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d0617d6..c613d3c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7156,12 +7156,13 @@ struct page * __weak } =20 struct page * __weak -follow_huge_pmd(struct mm_struct *mm, unsigned long address, - pmd_t *pmd, int flags) +follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address, int= flags) { + struct hstate *h =3D hstate_vma(vma); + struct mm_struct *mm =3D vma->vm_mm; struct page *page =3D NULL; spinlock_t *ptl; - pte_t pte; + pte_t *ptep, pte; =20 /* * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via @@ -7171,17 +7172,15 @@ struct page * __weak return NULL; =20 retry: - ptl =3D pmd_lockptr(mm, pmd); - spin_lock(ptl); - /* - * make sure that the address range covered by this pmd is not - * unmapped from other threads. - */ - if (!pmd_huge(*pmd)) - goto out; - pte =3D huge_ptep_get((pte_t *)pmd); + ptep =3D huge_pte_offset(mm, address, huge_page_size(h)); + if (!ptep) + return NULL; + + ptl =3D huge_pte_lock(h, mm, ptep); + pte =3D huge_ptep_get(ptep); if (pte_present(pte)) { - page =3D pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT); + page =3D pte_page(pte) + + ((address & ~huge_page_mask(h)) >> PAGE_SHIFT); /* * try_grab_page() should always succeed here, because: a) we * hold the pmd (ptl) lock, and b) we've just checked that the @@ -7197,7 +7196,7 @@ struct page * __weak } else { if (is_hugetlb_entry_migration(pte)) { spin_unlock(ptl); - __migration_entry_wait_huge((pte_t *)pmd, ptl); + __migration_entry_wait_huge(ptep, ptl); goto retry; } /* --=20 1.8.3.1