From patchwork Thu Feb 4 18:34:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12068441 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 364F1C433DB for ; Thu, 4 Feb 2021 19:16:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2E2364F38 for ; Thu, 4 Feb 2021 19:16:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239711AbhBDTQK (ORCPT ); Thu, 4 Feb 2021 14:16:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238673AbhBDSgT (ORCPT ); Thu, 4 Feb 2021 13:36:19 -0500 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83A0FC0617AB for ; Thu, 4 Feb 2021 10:34:52 -0800 (PST) Received: by mail-qt1-x84a.google.com with SMTP id d1so3284903qtp.11 for ; Thu, 04 Feb 2021 10:34:52 -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=BOdWGt2YrrFhUAh6Oya9odQ31xPXJajGw7XfNah1Ei0=; b=NBHdLCMVmjlgN5mUcDN7btxS+7ZLWcclBrRA56QJlXrMR8QRMxe4LKcc+rDaJR88Tg 81ZpUhmRyV+2iRs9b9i6X1F53gwpkWEkrPHiso9lwqtE01nZ0LC76zIowyeGwRQger9n MvN1CUkSc5RzCH3+1uJPnTf4lcAKThO0g7tGROkLDYgTOlEt+CYUjMazGvYBxhzJ26is 2gH5HlvO0XbpfhMs2p9bBdRgOCjFHHwlv8y9M7F5y30awvPM3pYsdA3nlMCVnO+SfpbC VJuVKmjkYK4vCc8vvFkmNhpnzIoB+2Lu2ef0b8fXz1jWw9ZJYS+CaSQD16ThR+WRoF/o 1JOQ== 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=BOdWGt2YrrFhUAh6Oya9odQ31xPXJajGw7XfNah1Ei0=; b=iELirD1UYImON3Bce4xMplorvMdbT0ZlCIA0PKHe1m4e0K5YesJyqfwCxmz3xq6lUu s5kS6sFPOfqPMiymA80fq+uRdE4fKI95lG2Gtvy5+a/c08xlFUW1lWRD5Zu39Cvtw5v2 4nww1idFk/8xgducaK8A9o3V13a6h8uu3psNyQzBjlH/ERoDDR7Wpw+B3nwuLwqN+0w4 sCpUn81b6PLpXSREGVBaTAC3O+LTwZu9zGePju1rzxFtbshUU5WMfBlCC9F/L2CwDV6t E44Sj6bBLS6RCNCniB1wGqBozl40/nJxkK7YXl53g997zx1S86qTfb8UD+7hEk3Samxe MomQ== X-Gm-Message-State: AOAM531JUKzpAAy2o/FXQDgC5ThRledkTKGoSjdS0SWJ39UD+dGQ4V0j GstQUjy0joXFMO6AmVaaL2nUukzGaZQ44/6e2Oj8 X-Google-Smtp-Source: ABdhPJyPb3Mlg/0ElAXzwxLs8sVTCzLB5QqJgGLurcVZpTtQkepWRndQWdvko4eXoVcaKAI92jkYW/tc6Gcw4S4Evpba Sender: "axelrasmussen via sendgmr" X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:b001:12c1:dc19:2089]) (user=axelrasmussen job=sendgmr) by 2002:a05:6214:2ee:: with SMTP id h14mr785467qvu.34.1612463691582; Thu, 04 Feb 2021 10:34:51 -0800 (PST) Date: Thu, 4 Feb 2021 10:34:27 -0800 In-Reply-To: <20210204183433.1431202-1-axelrasmussen@google.com> Message-Id: <20210204183433.1431202-5-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210204183433.1431202-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog Subject: [PATCH v4 04/10] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp 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 for hugetlbfs is racy with userfaultfd-wp because userfaultfd-wp is always based on pgtable entries, so they cannot be shared. Walk the hugetlb range and unshare all such mappings if there is, right before UFFDIO_REGISTER will succeed and return to userspace. This will pair with want_pmd_share() in hugetlb code so that huge pmd sharing is completely disabled for userfaultfd-wp registered range. Signed-off-by: Peter Xu Signed-off-by: Axel Rasmussen --- fs/userfaultfd.c | 48 ++++++++++++++++++++++++++++++++++++ include/linux/mmu_notifier.h | 1 + 2 files changed, 49 insertions(+) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 894cc28142e7..a0f66e12026b 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -1190,6 +1191,50 @@ static ssize_t userfaultfd_read(struct file *file, char __user *buf, } } +/* + * This function will unconditionally remove all the shared pmd pgtable entries + * within the specific vma for a hugetlbfs memory range. + */ +static void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) +{ +#ifdef CONFIG_HUGETLB_PAGE + struct hstate *h = hstate_vma(vma); + unsigned long sz = huge_page_size(h); + struct mm_struct *mm = vma->vm_mm; + struct mmu_notifier_range range; + unsigned long address; + spinlock_t *ptl; + pte_t *ptep; + + if (!(vma->vm_flags & VM_MAYSHARE)) + return; + + /* + * No need to call adjust_range_if_pmd_sharing_possible(), because + * we're going to operate on the whole vma + */ + mmu_notifier_range_init(&range, MMU_NOTIFY_HUGETLB_UNSHARE, + 0, vma, mm, vma->vm_start, vma->vm_end); + mmu_notifier_invalidate_range_start(&range); + i_mmap_lock_write(vma->vm_file->f_mapping); + for (address = vma->vm_start; address < vma->vm_end; address += sz) { + ptep = huge_pte_offset(mm, address, sz); + if (!ptep) + continue; + ptl = huge_pte_lock(h, mm, ptep); + huge_pmd_unshare(mm, vma, &address, ptep); + spin_unlock(ptl); + } + flush_hugetlb_tlb_range(vma, vma->vm_start, vma->vm_end); + i_mmap_unlock_write(vma->vm_file->f_mapping); + /* + * No need to call mmu_notifier_invalidate_range(), see + * Documentation/vm/mmu_notifier.rst. + */ + mmu_notifier_invalidate_range_end(&range); +#endif +} + static void __wake_userfault(struct userfaultfd_ctx *ctx, struct userfaultfd_wake_range *range) { @@ -1448,6 +1493,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, vma->vm_flags = new_flags; vma->vm_userfaultfd_ctx.ctx = ctx; + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) + hugetlb_unshare_all_pmds(vma); + skip: prev = vma; start = vma->vm_end; diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index b8200782dede..ff50c8528113 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -51,6 +51,7 @@ enum mmu_notifier_event { MMU_NOTIFY_SOFT_DIRTY, MMU_NOTIFY_RELEASE, MMU_NOTIFY_MIGRATE, + MMU_NOTIFY_HUGETLB_UNSHARE, }; #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)