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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0821C7EE25 for ; Fri, 28 Apr 2023 15:24:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346401AbjD1PYa (ORCPT ); Fri, 28 Apr 2023 11:24:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346374AbjD1PY1 (ORCPT ); Fri, 28 Apr 2023 11:24:27 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 662475FC7 for ; Fri, 28 Apr 2023 08:23:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1682695415; 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=xNqQu/Hbgh8GgG/TaR2UQBBPYePy9tTL0DFgLY8LdrU=; b=ML+bEd2uqQF2mEPpifoZPqZcHUoCUQjeUJuAhtGvXo0DjrvcggrLWnMSMMMuoQn4c7XHHB KNmAn4P4foC4wDMAIOrh3ur6oYsg0KQ8ox/SvOptb0JVUw4tZjAezMAYmHVyJRD+UBdisz OAEUKvOl3Bft8brNPq0qj3Mnw0A2I0o= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-609-JZtnuQ3pNguXYYP_XUofEA-1; Fri, 28 Apr 2023 11:23:33 -0400 X-MC-Unique: JZtnuQ3pNguXYYP_XUofEA-1 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-2fbb99cb303so3721587f8f.1 for ; Fri, 28 Apr 2023 08:23:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682695413; x=1685287413; h=content-transfer-encoding:in-reply-to:subject:organization :references:cc:to:from:content-language:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=xNqQu/Hbgh8GgG/TaR2UQBBPYePy9tTL0DFgLY8LdrU=; b=ij5lGN9XD/DJb30n1BWNeK4G9XF6zZZlv6EHD6mSFqI5EMOtfWQ2+/2nm4I/NW6k2j QHodEFfr8+pc+ZonIexAHzizyedYrq0qhrpCfQNHjpa9OmQ2wUskMA1ylJ2xoOlTRnD9 3ivn9w3jw1wK4dWU/YzOPh+iceLOFK67Iwa4hHdXk8hpt0EdeuuyUe5lmuiS3VIhNHJY Ng5l8x+eeUDH+/WLt+rPLGJFdHq2g3G8BwHBEeJWgtsOI1M/y5XCwBOxPgbzIWeGviRt CqwHAYH9068B/tadCU3evm0dQdV6Fy5NveVOnKe/j5/+HupOjQCaGhDDmhizbKmaIVsN 43wQ== X-Gm-Message-State: AC+VfDwRa4Q9bi7ghVy/u6ES9t3cH0mV2+rAnfBCOUqcTIfuOpwscGMe CrP+QtPeed/itDhmbW5hA//273bVm5tu7OfWK9pqdPQviVRaNPLX61D4xvmwRD7Lx+8cwFW30J3 tKJyI2MOolBsjmhENLEhsCIl/EZ2K6g== X-Received: by 2002:a05:6000:1148:b0:304:7159:d3e4 with SMTP id d8-20020a056000114800b003047159d3e4mr4054758wrx.44.1682695412809; Fri, 28 Apr 2023 08:23:32 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ7m7lYREqwJwCW0J3nLemNcIH2KdfBgyx6gX0Qrhp/YfT+ZQtoJy3PoVU25XYCmL9JQIphxhg== X-Received: by 2002:a05:6000:1148:b0:304:7159:d3e4 with SMTP id d8-20020a056000114800b003047159d3e4mr4054718wrx.44.1682695412463; Fri, 28 Apr 2023 08:23:32 -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 a18-20020a056000101200b002e61e002943sm21368158wrx.116.2023.04.28.08.23.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Apr 2023 08:23:31 -0700 (PDT) Message-ID: <400da248-a14e-46a4-420a-a3e075291085@redhat.com> Date: Fri, 28 Apr 2023 17:23:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Content-Language: en-US From: David Hildenbrand To: Jason Gunthorpe Cc: Lorenzo Stoakes , 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> Organization: Red Hat Subject: Re: [PATCH v5] mm/gup: disallow GUP writing to file-backed mappings by default In-Reply-To: <094d2074-5b69-5d61-07f7-9f962014fa68@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org >> >> 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. Of course, this would prevent hugetlb/shmem from getting pinned writable during gup-fast. Unless we're able to whitelist them somehow in there. For FOLL_LONGTERM it might fairly uncontroversial. For everything else I'm not sure if there could be undesired side-effects. -- Thanks, David / dhildenb