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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02CD1C636CC for ; Mon, 13 Feb 2023 15:12:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8F7636B0071; Mon, 13 Feb 2023 10:12:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 87FCB6B0072; Mon, 13 Feb 2023 10:12:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F9D66B0073; Mon, 13 Feb 2023 10:12:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 5CCFA6B0071 for ; Mon, 13 Feb 2023 10:12:32 -0500 (EST) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 03FA11C6161 for ; Mon, 13 Feb 2023 15:12:31 +0000 (UTC) X-FDA: 80462610144.03.883E45B Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf24.hostedemail.com (Postfix) with ESMTP id 354FE18001E for ; Mon, 13 Feb 2023 15:12:27 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=IXRykynP; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676301148; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Q44SzMdooSXMXJeRZpOwcElNDmoy9RihuEQ1QO7JM9c=; b=sdgAiG4ldTXWM9tqu3lf/OaU+fKqFGkLuStK13ZO+hlIDyjrbCGV10zpUDZvgXqEpSIgqm 2RkFK0m56ZZLpjiipHxlu/TGjAhhVWGUgwD4+tVQXXHLoJMmOJRanQT3ksw31PuM6vppHy 4pThSLJq1YW6OFLI+K5ltjTMZuhzBVc= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=IXRykynP; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676301148; a=rsa-sha256; cv=none; b=Dq/ZQ701lqWIqhSiWVtPPUiVZ4cLUxoMcxwTza2VxFbunBPq3CBdQIBxvTEO6/xu58gMoS VVaEmMhXw2LeAS0TFtpOSgU2bOXi3Z+BXXyM0oVCBDrgX+nGMDpsTFHAyzdpLVuFY0cHXT NOQi8jWBZ0A6UmzgocMB2nnrL0Kd71Y= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676301146; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Q44SzMdooSXMXJeRZpOwcElNDmoy9RihuEQ1QO7JM9c=; b=IXRykynPvp/4Avb1QIbdS89wbkF6yvdTmWQjWpWIzfoU1/L4bQa/edpAgYTWynQpjqnpZ2 G8b/Ix13B4nJYZxZW6fDi2WcWafwIvCol4z3vwo7ueJJ3FqrVa2XEgYHTPs3CL8/bWa7gM uvwj5TzkLEbMqalC8nJ9NbSdInXp0is= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-642-HuJ6cRKHOlyJ1zCinjyxgA-1; Mon, 13 Feb 2023 10:12:23 -0500 X-MC-Unique: HuJ6cRKHOlyJ1zCinjyxgA-1 Received: by mail-wm1-f71.google.com with SMTP id s11-20020a05600c384b00b003dffc7343c3so6304485wmr.0 for ; Mon, 13 Feb 2023 07:12:23 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Q44SzMdooSXMXJeRZpOwcElNDmoy9RihuEQ1QO7JM9c=; b=tSlEJo6FbyoBUKZNsJXXl3o3O/9LP3+BTINuPeYCxlH/gc+fRSdFAKA0QCHufK3WJK BeJspHHnISQE2w/BTFPWgKZjCbtJgGbRZxd2Hjyc204YEa4xScui113TnzXWXGU/QY7O O57iMkN+oiuwLYXbagroCAZtu/hlWUiyVbh9JLv095MGWjlZRy0vRLuibOCBiUxuEsMv ntqx6O0OwNCl4Q0imKhAE6+nRLpp4dZuFJnoalfkq2mKTQ73/dO1jZ2rAEgGa1TRoha1 J+KgvxPynsFUjjkKiE23fJpemoFB2Irto3qhB5xK+qa7OMuatywbJXlyCGHyI4jmmH5K a+cw== X-Gm-Message-State: AO0yUKUu6p4KMzyHF3+CAnWAD8CywuGHks/ytsj93MLhsyr4qNYXvhnY x3haYxNbmy3CMiNtwhtYkNO9OYdglg+/vXEcVfygZwH+phF6wZRF7kGCD4YWeXiT4eKC0cojl+h VXVkHmNhDSkY= X-Received: by 2002:a05:600c:601a:b0:3dc:42e7:f626 with SMTP id az26-20020a05600c601a00b003dc42e7f626mr19173260wmb.26.1676301142297; Mon, 13 Feb 2023 07:12:22 -0800 (PST) X-Google-Smtp-Source: AK7set+jSOVTfdI4/1RwvFCtOf9bbApfXLC1oIVs5XF/of2Pf26darj2/ZKwUYO/IFWKiFJxUX7bWA== X-Received: by 2002:a05:600c:601a:b0:3dc:42e7:f626 with SMTP id az26-20020a05600c601a00b003dc42e7f626mr19173242wmb.26.1676301142038; Mon, 13 Feb 2023 07:12:22 -0800 (PST) Received: from ?IPV6:2003:cb:c705:6d00:5870:9639:1c17:8162? (p200300cbc7056d00587096391c178162.dip0.t-ipconnect.de. [2003:cb:c705:6d00:5870:9639:1c17:8162]) by smtp.gmail.com with ESMTPSA id k21-20020a05600c1c9500b003dd1c45a7b0sm14991291wms.23.2023.02.13.07.12.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Feb 2023 07:12:21 -0800 (PST) Message-ID: <92597a6b-3c4e-ad11-a5ba-f7d3919b6ba1@redhat.com> Date: Mon, 13 Feb 2023 16:12:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH] mm/userfaultfd: Support operation on multiple VMAs To: Muhammad Usama Anjum , peterx@redhat.com, Andrew Morton Cc: kernel@collabora.com, Paul Gofman , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230213104323.1792839-1-usama.anjum@collabora.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 354FE18001E X-Stat-Signature: z8dop4u8bubejesshji6eoxu17tn83q6 X-HE-Tag: 1676301147-85010 X-HE-Meta: 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 jCpZ6/EY 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 13.02.23 16:04, Muhammad Usama Anjum wrote: > Hi David, > > Thank you for quick review! > > On 2/13/23 4:44 PM, David Hildenbrand wrote: >> On 13.02.23 11:43, Muhammad Usama Anjum wrote: >>> mwriteprotect_range() errors out if [start, end) doesn't fall in one >>> VMA. We are facing a use case where multiple VMAs are present in one >>> range of interest. For example, the following pseudocode reproduces the >>> error which we are trying to fix: >>> >>> - Allocate memory of size 16 pages with PROT_NONE with mmap >>> - Register userfaultfd >>> - Change protection of the first half (1 to 8 pages) of memory to >>>    PROT_READ | PROT_WRITE. This breaks the memory area in two VMAs. >>> - Now UFFDIO_WRITEPROTECT_MODE_WP on the whole memory of 16 pages errors >>>    out. >>> >>> This is a simple use case where user may or may not know if the memory >>> area has been divided into multiple VMAs. >>> >>> Reported-by: Paul Gofman >>> Signed-off-by: Muhammad Usama Anjum >>> --- >>>   mm/userfaultfd.c | 36 +++++++++++++++++++----------------- >>>   1 file changed, 19 insertions(+), 17 deletions(-) >>> >>> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c >>> index 65ad172add27..46e0a014af68 100644 >>> --- a/mm/userfaultfd.c >>> +++ b/mm/userfaultfd.c >>> @@ -738,9 +738,11 @@ int mwriteprotect_range(struct mm_struct *dst_mm, >>> unsigned long start, >>>               unsigned long len, bool enable_wp, >>>               atomic_t *mmap_changing) >>>   { >>> +    unsigned long end = start + len; >>>       struct vm_area_struct *dst_vma; >>>       unsigned long page_mask; >>>       int err; >>> +    VMA_ITERATOR(vmi, dst_mm, start); >>>         /* >>>        * Sanitize the command parameters: >>> @@ -762,26 +764,26 @@ int mwriteprotect_range(struct mm_struct *dst_mm, >>> unsigned long start, >>>       if (mmap_changing && atomic_read(mmap_changing)) >>>           goto out_unlock; >>>   -    err = -ENOENT; >>> -    dst_vma = find_dst_vma(dst_mm, start, len); >>> - >>> -    if (!dst_vma) >>> -        goto out_unlock; >>> -    if (!userfaultfd_wp(dst_vma)) >>> -        goto out_unlock; >>> -    if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) >>> -        goto out_unlock; >>> +    for_each_vma_range(vmi, dst_vma, end) { >>> +        err = -ENOENT; >>>   -    if (is_vm_hugetlb_page(dst_vma)) { >>> -        err = -EINVAL; >>> -        page_mask = vma_kernel_pagesize(dst_vma) - 1; >>> -        if ((start & page_mask) || (len & page_mask)) >>> -            goto out_unlock; >>> -    } >>> +        if (!dst_vma->vm_userfaultfd_ctx.ctx) >>> +            break; >>> +        if (!userfaultfd_wp(dst_vma)) >>> +            break; >>> +        if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) >>> +            break; >>>   -    uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); >>> +        if (is_vm_hugetlb_page(dst_vma)) { >>> +            err = -EINVAL; >>> +            page_mask = vma_kernel_pagesize(dst_vma) - 1; >>> +            if ((start & page_mask) || (len & page_mask)) >>> +                break; >>> +        } >>>   -    err = 0; >>> +        uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); >> >> I suspect you should be adjusting the range to only cover that specific VMA >> here. > Sorry, you are right. I don't know why it is still working with the > blunder. Will send a v2. Maybe worth adding some sanity checks (VM_WARN_ONCE()) in there (e.g., change_protection()) to catch that. -- Thanks, David / dhildenb