From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2078DC433E0 for ; Thu, 18 Feb 2021 21:57:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF2F264E38 for ; Thu, 18 Feb 2021 21:57:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229945AbhBRV5e (ORCPT ); Thu, 18 Feb 2021 16:57:34 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:21442 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229908AbhBRV5V (ORCPT ); Thu, 18 Feb 2021 16:57:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613685355; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=e4OLUk0Jy8zIZlRHoRelkknb6fgRUan1/BmpVqTVRpo=; b=YPebaQdqYu38hgBKSGJnMSd0W1C6mxkLyZBRrrYYfACaeCrwT0v7LxMoMRa1ZMtH46MHJB EnxG9JFw5jXDXT0+5R+lCKVRk24Txv3cCDU4czvmmSS9DG3M7AI5wn2vghoyDAQnISz107 ZxUMoGuMjgHfJeTuwCqFh/VlGn4QLWQ= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-547-rXNQcgXdPsyuHe5c1KTRLA-1; Thu, 18 Feb 2021 16:55:54 -0500 X-MC-Unique: rXNQcgXdPsyuHe5c1KTRLA-1 Received: by mail-qv1-f72.google.com with SMTP id eu6so2017406qvb.3 for ; Thu, 18 Feb 2021 13:55:54 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=e4OLUk0Jy8zIZlRHoRelkknb6fgRUan1/BmpVqTVRpo=; b=m45Wc1mv090Vu3aC/mJgbGjfvYc1v0cT85+rVPCKnqEV//3NxZ4d06X+AAoO1BoMOS IiiK9BhSMSgGPFM5RCK63Caxt7jgGSi33WD+/jdPHEBNqf1LmDSdws7RkugsDYhkiW84 WMYelBpATWod9MXnArJu6qpVS1bCbaSZVFbj57hMR50CN9OYpnMSgOCK8oRcJHgOqzs0 YLCsVZag8wLMnM85jRGktSNVUf4xL/dVIy1sm5+2Eeqox1Id1sal5PwhlS81lzY78CZX faSNUhsGXki95wM4IF9OjEK1Ld8L5KZHO/IVEiTRArYk3IB/PnRNe8qjMHJkTEBJIY+1 MmQQ== X-Gm-Message-State: AOAM5320wpA/tshnsmAc//NWMOCc8vezGFWfmhcni/J/qhI3ZcH38S8C b/d8rqQFt3jNlncajJ+o+FdTYu1QiDLRgK6nvGU8NhkHiLVrQqJfYOByFz4bCSNo3GerpAyi09m eChGr4TbkDiQ3gXKOl/MytYC1R+HLEK7Y63lwFXjU+X2+AnRwKy1/Tg08WIEw/bCP7dom3/V9lw == X-Received: by 2002:a05:620a:227:: with SMTP id u7mr6649941qkm.226.1613685353188; Thu, 18 Feb 2021 13:55:53 -0800 (PST) X-Google-Smtp-Source: ABdhPJzPwEwqxlrFOFzSQ7p6jnGuKozTyPWx/xZeRZ1As4UoBD2Ea1DWzSKkNh01txbsI90r/Aw5MA== X-Received: by 2002:a05:620a:227:: with SMTP id u7mr6649915qkm.226.1613685352896; Thu, 18 Feb 2021 13:55:52 -0800 (PST) Received: from xz-x1.redhat.com (bras-vprn-toroon474qw-lp130-20-174-93-89-182.dsl.bell.ca. [174.93.89.182]) by smtp.gmail.com with ESMTPSA id c126sm4863324qkg.16.2021.02.18.13.55.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Feb 2021 13:55:52 -0800 (PST) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Mike Kravetz , Andrew Morton , Mike Rapoport , Andrea Arcangeli , peterx@redhat.com, Axel Rasmussen , "Kirill A . Shutemov" , Matthew Wilcox Subject: [PATCH v3 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Date: Thu, 18 Feb 2021 16:55:51 -0500 Message-Id: <20210218215551.10612-1-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210218215434.10203-1-peterx@redhat.com> References: <20210218215434.10203-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Huge pmd sharing could bring problem to userfaultfd. The thing is that userfaultfd is running its logic based on the special bits on page table entries, however the huge pmd sharing could potentially share page table entries for different address ranges. That could cause issues on either: - When sharing huge pmd page tables for an uffd write protected range, the newly mapped huge pmd range will also be write protected unexpectedly, or, - When we try to write protect a range of huge pmd shared range, we'll first do huge_pmd_unshare() in hugetlb_change_protection(), however that also means the UFFDIO_WRITEPROTECT could be silently skipped for the shared region, which could lead to data loss. Since at it, a few other things are done altogether: - Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because that's definitely something that arch code would like to use too - ARM64 currently directly check against CONFIG_ARCH_WANT_HUGE_PMD_SHARE when trying to share huge pmd. Switch to the want_pmd_share() helper. Since at it, move vma_shareable() from huge_pmd_share() into want_pmd_share(). Reviewed-by: Mike Kravetz Reviewed-by: Axel Rasmussen Signed-off-by: Peter Xu --- arch/arm64/mm/hugetlbpage.c | 3 +-- include/linux/hugetlb.h | 2 ++ include/linux/userfaultfd_k.h | 9 +++++++++ mm/hugetlb.c | 20 ++++++++++++++------ 4 files changed, 26 insertions(+), 8 deletions(-) diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 6e3bcffe2837..58987a98e179 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -284,8 +284,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, */ ptep = pte_alloc_map(mm, pmdp, addr); } else if (sz == PMD_SIZE) { - if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && - pud_none(READ_ONCE(*pudp))) + if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp))) ptep = huge_pmd_share(mm, vma, addr, pudp); else ptep = (pte_t *)pmd_alloc(mm, pudp, addr); diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index a6113fa6d21d..bc86f2f516e7 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -950,4 +950,6 @@ static inline __init void hugetlb_cma_check(void) } #endif +bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr); + #endif /* _LINUX_HUGETLB_H */ diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index a8e5f3ea9bb2..c63ccdae3eab 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -52,6 +52,15 @@ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx; } +/* + * Never enable huge pmd sharing on uffd-wp registered vmas, because uffd-wp + * protect information is per pgtable entry. + */ +static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma) +{ + return vma->vm_flags & VM_UFFD_WP; +} + static inline bool userfaultfd_missing(struct vm_area_struct *vma) { return vma->vm_flags & VM_UFFD_MISSING; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 07bb9bdc3282..8e8e2f3dfe06 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5292,6 +5292,18 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) return false; } +bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) +{ +#ifndef CONFIG_ARCH_WANT_HUGE_PMD_SHARE + return false; +#endif +#ifdef CONFIG_USERFAULTFD + if (uffd_disable_huge_pmd_share(vma)) + return false; +#endif + return vma_shareable(vma, addr); +} + /* * Determine if start,end range within vma could be mapped by shared pmd. * If yes, adjust start and end to cover range associated with possible @@ -5346,9 +5358,6 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma, pte_t *pte; spinlock_t *ptl; - if (!vma_shareable(vma, addr)) - return (pte_t *)pmd_alloc(mm, pud, addr); - i_mmap_assert_locked(mapping); vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) { if (svma == vma) @@ -5412,7 +5421,7 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE; return 1; } -#define want_pmd_share() (1) + #else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct vma, unsigned long addr, pud_t *pud) @@ -5430,7 +5439,6 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, unsigned long *start, unsigned long *end) { } -#define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB @@ -5452,7 +5460,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, pte = (pte_t *)pud; } else { BUG_ON(sz != PMD_SIZE); - if (want_pmd_share() && pud_none(*pud)) + if (want_pmd_share(vma, addr) && pud_none(*pud)) pte = huge_pmd_share(mm, vma, addr, pud); else pte = (pte_t *)pmd_alloc(mm, pud, addr); -- 2.26.2