From patchwork Wed Feb 10 21:21:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12081763 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, 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,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 D34D4C433DB for ; Wed, 10 Feb 2021 21:23:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A430764ED3 for ; Wed, 10 Feb 2021 21:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233521AbhBJVXK (ORCPT ); Wed, 10 Feb 2021 16:23:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233358AbhBJVWv (ORCPT ); Wed, 10 Feb 2021 16:22:51 -0500 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [IPv6:2607:f8b0:4864:20::1049]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17C56C06178C for ; Wed, 10 Feb 2021 13:22:11 -0800 (PST) Received: by mail-pj1-x1049.google.com with SMTP id y22so2241317pjp.5 for ; Wed, 10 Feb 2021 13:22:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=hnaAeM5s+w8DJX76RPfJONuTnc8xLec37Vehd5HeKu4=; b=rT9xRNa1VIiUFPnpy4os5esD59yyOdCLADkE4Mt5k31roGAL/DqU3FLcMg6tUIty9o q6ErhrLk1CSPG6B5gBI4Vm1dKANSxKMPj6RPuZunzPWgZxxcvdzMfrhFeEpJ5JzVJIHE 6gxDrphQPYCfBBQFIEHVuC0Xpuc8r2UaUydFrYogt68o05NBpU/i2sHIIy4JJN9Bzcx2 MLtjyveEBrlyiV2AyFeva0A2EHcAlM6VAhdaI+XGccYzsB4Ks9rrMgN9SBJm0m4B/Hxg fEWIfjXl6UrWz/RZjEF5vaC2Bm1A3VFg2Odya5SIp4xbHT8IzbXYKchCftxzIwy0Ks+x u3ew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=hnaAeM5s+w8DJX76RPfJONuTnc8xLec37Vehd5HeKu4=; b=TmLfxIw1Kyp6Si3cPQDTk9pEuQFMdqct65TgsM5COa5EHwRcMJKRCZ8bE53H4r8wOw +lSFEh2Ozi3b+WG7uNgxGgb/ONykPLuPKWXIXTGyPzydw+gEoILGeQPz4knqS9e03wNL E8n1G9+ZEre6F+N5XiURtR/ECwpgwFphtnW+j7uJlhLPo834VDl37b53vjCrk0fNjCXL s4YnBDWZ46ZtAES9P1VKNM+MkAI5C7tHhjYbaqpo+nMuP+4UYuVXm4TJ+8ujD2lLISuC Qb11zaCzipiQfNTXQ/H9sHPFFfh9A9oJ4H3HX/U3o/lOS/1kKOAvjZO1RzPefmyRobHP kwrA== X-Gm-Message-State: AOAM532OEfHtTkQfAD8rKu0XMG45Rornflfn3vRgzqpE69q29u7DG7Mp DNCMxD8h/4FVZuFVQ54tVUHzEIEa57x+LQoRr/uj X-Google-Smtp-Source: ABdhPJwMBNBgVFnVfutXp93h4VFnNAN1Zy0Grp7R/VpQFaqM0x0RCowKe+s4eVo9U3hnShVH8b//2tNlEpLT0e9b208b Sender: "axelrasmussen via sendgmr" X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:94ee:de01:168:9f20]) (user=axelrasmussen job=sendgmr) by 2002:a17:902:cd13:b029:e2:efc5:d33d with SMTP id g19-20020a170902cd13b02900e2efc5d33dmr4879127ply.61.1612992130552; Wed, 10 Feb 2021 13:22:10 -0800 (PST) Date: Wed, 10 Feb 2021 13:21:52 -0800 In-Reply-To: <20210210212200.1097784-1-axelrasmussen@google.com> Message-Id: <20210210212200.1097784-3-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210210212200.1097784-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [PATCH v5 02/10] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled From: Axel Rasmussen To: Alexander Viro , Alexey Dobriyan , Andrea Arcangeli , Andrew Morton , Anshuman Khandual , Catalin Marinas , Chinwen Chang , Huang Ying , Ingo Molnar , Jann Horn , Jerome Glisse , Lokesh Gidra , "Matthew Wilcox (Oracle)" , Michael Ellerman , " =?utf-8?q?Michal_Koutn=C3=BD?= " , Michel Lespinasse , Mike Kravetz , Mike Rapoport , Nicholas Piggin , Peter Xu , Shaohua Li , Shawn Anastasio , Steven Rostedt , Steven Price , Vlastimil Babka Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Adam Ruprecht , Axel Rasmussen , Cannon Matthews , "Dr . David Alan Gilbert" , David Rientjes , Mina Almasry , Oliver Upton Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Peter Xu 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(). Signed-off-by: Peter Xu Signed-off-by: Axel Rasmussen --- 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 ca6e5ba56f73..d971e7efd17d 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -1030,4 +1030,6 @@ 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 32d4d2e277ad..5710286e1984 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5245,6 +5245,18 @@ 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 @@ -5301,9 +5313,6 @@ 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) @@ -5367,7 +5376,7 @@ 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) @@ -5385,7 +5394,6 @@ 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 @@ -5407,7 +5415,7 @@ 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);