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 2B3D0C77B60 for ; Fri, 28 Apr 2023 16:03:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BBAA26B0085; Fri, 28 Apr 2023 12:03:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B6AB06B0087; Fri, 28 Apr 2023 12:03:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A0B906B0088; Fri, 28 Apr 2023 12:03:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 92DC46B0085 for ; Fri, 28 Apr 2023 12:03:07 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 632DF1A02D7 for ; Fri, 28 Apr 2023 16:03:07 +0000 (UTC) X-FDA: 80731268814.30.511AB17 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf19.hostedemail.com (Postfix) with ESMTP id 06C571A0025 for ; Fri, 28 Apr 2023 16:03:04 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HRCkt7TJ; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf19.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1682697785; 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=ygEgijBc1IgIq8cFGjEh4tdLm5WBe48ZCNtdfsoShbQ=; b=zAiQruk2Kov4msyqc0VzosKVfeBrMdiq7XIwH/l2IkX84BHiwHA+/MMdn7T42lbDj2S9bJ 08BqO0ZkG00O2NBRHZmpwGRh2ZLbndWnNsQn3oHyDNIdaluZUnHskaNUEJKxCoS5PtxfNG HTiuXQ2vVHU+tutW92fMC22BHLd+jXg= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HRCkt7TJ; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf19.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1682697785; a=rsa-sha256; cv=none; b=G9t3UgU8fqgM0ZjsOpCiVhv52hN0wkTSE7W/TvRfb1ncjG4/XQWeMN78hryaaaZ+G+94Pf BnyykjybGHMGl8Zz6i6Kb93U2BbkAnX8ZIO6niBQ0K4wxeoSaO7gLmc6R8SpeVsklaWV0G z2lkMbBcZlrWT0Qhv0mUcNd5eGwUnlQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1682697784; 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=ygEgijBc1IgIq8cFGjEh4tdLm5WBe48ZCNtdfsoShbQ=; b=HRCkt7TJT9S3o7ed/tctIRItTPsZ2hTfkHLXMXbFoks88hz7aFjZk6evjcJhgZqFeCWwVh mSBlx1zdIsF47T8z3p/CnfQZDdJ390/niD2WL9BX61QDmcpwn26cCEEc26r8wEvDXVM59Q jENFgPs/BMgpbUOdlyXvUnvzx60Skew= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-633-rGooJ6ajOvGostLec3GgsQ-1; Fri, 28 Apr 2023 12:03:03 -0400 X-MC-Unique: rGooJ6ajOvGostLec3GgsQ-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-2f625d521abso5860937f8f.3 for ; Fri, 28 Apr 2023 09:03:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682697779; x=1685289779; 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=ygEgijBc1IgIq8cFGjEh4tdLm5WBe48ZCNtdfsoShbQ=; b=Cp5giBIhqsg7RJnHHIXR9n+CSv1WAfwp306p7z/+r/3IdmD3pynqTMiarI40yw1k2r ULTBiOdODPMl7JWR02sYmrhWunUt3hhb+EKEYTCYQmbBAF52GrlO1Fpw1jDtIDKl9zMl jxfTRlRsYo/pYy7MZl4q/SRaSCYoHqiLPJsQITSkgCasbVFO9KVZCLAh1Ryk6/5kTyHf +FpNXovwoejsM56M8PPPAF8Or7lunD59QXQ6gYQibxP75MfmEmCGgmjdF3k99rQVIx3A zD7RHODAbIerQzPFfzMnWK2h0wwec0Ic3obSGJppVaYwupHaeO5sRdFKF1Ngphbc3D+8 YNSQ== X-Gm-Message-State: AC+VfDwxdqsE78ZlFmqgXk3x5oQXLA3B1B3ATdW8KDMwHR363WIyD0lj AXoOasAEZcZY7ksahWHemnADBlw0fvEzcONLJ3fzLe9EurBZ77asNLmy2G6gb5qYDPc2DCR98pC aePSxclsNWTA= X-Received: by 2002:a5d:595a:0:b0:304:7237:729a with SMTP id e26-20020a5d595a000000b003047237729amr4261542wri.67.1682697779317; Fri, 28 Apr 2023 09:02:59 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ7Ku7Blfk4RQb9TUtQ5+s7GnYVImteWm54uw3a9dTygTNMWUmW0JJgkbiWnH2eUAqvpUaXDng== X-Received: by 2002:a5d:595a:0:b0:304:7237:729a with SMTP id e26-20020a5d595a000000b003047237729amr4261467wri.67.1682697778920; Fri, 28 Apr 2023 09:02:58 -0700 (PDT) Received: from ?IPV6:2003:cb:c726:9300:1711:356:6550:7502? (p200300cbc72693001711035665507502.dip0.t-ipconnect.de. [2003:cb:c726:9300:1711:356:6550:7502]) by smtp.gmail.com with ESMTPSA id x8-20020a05600c21c800b003f2390bdd0csm16068630wmj.32.2023.04.28.09.02.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Apr 2023 09:02:58 -0700 (PDT) Message-ID: <0e6ef85d-d53a-c847-c70b-900eb925a413@redhat.com> Date: Fri, 28 Apr 2023 18:02:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v5] mm/gup: disallow GUP writing to file-backed mappings by default To: Peter Xu Cc: Lorenzo Stoakes , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Christian Brauner , Richard Cochran , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Oleg Nesterov , John Hubbard , Jan Kara , "Kirill A . Shutemov" , Pavel Begunkov , Mika Penttila , David Howells , Christoph Hellwig References: <6b73e692c2929dc4613af711bdf92e2ec1956a66.1682638385.git.lstoakes@gmail.com> <094d2074-5b69-5d61-07f7-9f962014fa68@redhat.com> <400da248-a14e-46a4-420a-a3e075291085@redhat.com> <077c4b21-8806-455f-be98-d7052a584259@lucifer.local> <62ec50da-5f73-559c-c4b3-bde4eb215e08@redhat.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: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 06C571A0025 X-Stat-Signature: t1amze8j9qxuzhepqpbbf7b7d3rs41xk X-HE-Tag: 1682697784-930777 X-HE-Meta: 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 7ArKbXIL jnp0LVUS+XBaESj5f2TdYvJTXQnxCKkXmWFwwMpQEwx5AksxMlL//YzklyK/qaPNRnjnyXwZGSYcNVCZ8Q5uCwg0kar1L9C/uE1mH5RgRg5OWLFplsTaDARj7liE0eWxvsHyecW8OgRkp8knddF43Vsd70xtsI8CvgTugtBobX4NgSFS9FKES5BN24fgWLhCZFqCUryoGwQ4ikas5twHU77YraSqPJ4LITum0DihyoBLYsYdsg2gPdiKNwCcVTAr9BDaA658+VQVdqtT4kZkzmV2Wt8DUuPxF7LycbNJ8d9bwflbAyCx2Ko15LUDHyBfsq5QbGvXJN5Ax/wa9E6QDZ0H9p0vDWY553mdnkQFOdryjZ9iikHfSj/QdOyefcaHe0s9rgC5wjH4M5EeB8FC5QQFYCYWBXt2LEfMr6scse2veG/8s5QxllttmsLkbwadFNyGp2/ViJuJnCbA= 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 28.04.23 17:56, Peter Xu wrote: > On Fri, Apr 28, 2023 at 05:34:35PM +0200, David Hildenbrand wrote: >> On 28.04.23 17:33, Lorenzo Stoakes wrote: >>> On Fri, Apr 28, 2023 at 05:23:29PM +0200, David Hildenbrand wrote: >>>>>> >>>>>> Security is the primary case where we have historically closed uAPI >>>>>> items. >>>>> >>>>> As this patch >>>>> >>>>> 1) Does not tackle GUP-fast >>>>> 2) Does not take care of !FOLL_LONGTERM >>>>> >>>>> I am not convinced by the security argument in regard to this patch. >>>>> >>>>> >>>>> If we want to sells this as a security thing, we have to block it >>>>> *completely* and then CC stable. >>>> >>>> Regarding GUP-fast, to fix the issue there as well, I guess we could do >>>> something similar as I did in gup_must_unshare(): >>>> >>>> If we're in GUP-fast (no VMA), and want to pin a !anon page writable, >>>> fallback to ordinary GUP. IOW, if we don't know, better be safe. >>> >>> How do we determine it's non-anon in the first place? The check is on the >>> VMA. We could do it by following page tables down to folio and checking >>> folio->mapping for PAGE_MAPPING_ANON I suppose? >> >> PageAnon(page) can be called from GUP-fast after grabbing a reference. See >> gup_must_unshare(). > > Hmm.. Is it a good idea at all to sacrifise all "!anon" fast-gups for this? > People will silently got degrade even on legal pins on shmem/hugetlb, I > think, which seems to be still a very major use case. > Right. Optimizing for hugetlb should be easy. Shmem is problematic. I once raised to John that PageAnonExclusive is essentially a "anon page is pinnable" flag. Too bad we don't have spare page flags ;) -- Thanks, David / dhildenb