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 1B0D1C77B61 for ; Mon, 24 Apr 2023 17:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231788AbjDXRtl (ORCPT ); Mon, 24 Apr 2023 13:49:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38450 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230525AbjDXRtj (ORCPT ); Mon, 24 Apr 2023 13:49:39 -0400 Received: from mail-pf1-x42d.google.com (mail-pf1-x42d.google.com [IPv6:2607:f8b0:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 850996A79 for ; Mon, 24 Apr 2023 10:49:38 -0700 (PDT) Received: by mail-pf1-x42d.google.com with SMTP id d2e1a72fcca58-63b57c49c4cso4071624b3a.3 for ; Mon, 24 Apr 2023 10:49:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1682358578; x=1684950578; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=edIyrpOkZxkR7qQPvMEjMBtYXDIPtOhEQ7kSltA2Y7E=; b=B0RGu9bSAOqeQFKM2kCfJoKnl08Vl+oe+fwmnFVAivzg30GMkKXPEJIoCB0NsHbaMh y1QOEsnnYJO/COyfiUTW2dtgpEZrqz2vLI1HRdIkW9hABd7zQuI3eeVtbR5A2iA6mCaV 5QBQkDfq+xdn7BOEA9dEj6QIjjHMU11j/zgdaVZsVhi8C2oRl6bFxT6thxHV49P2U8UL zYC+DjT2f/NHcPLoSAHdcnqWWaY/yPWwMTsi+NOz2XxNjs9qrmO2DZcxaSVTMPKUaaw8 WFfpAud6lL6IcXM5+aRHmp/yuX4VH+U0aJ4N7MhsIExmp9g+j5ts12kN96no48OTOYsl BwRQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682358578; x=1684950578; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=edIyrpOkZxkR7qQPvMEjMBtYXDIPtOhEQ7kSltA2Y7E=; b=O2DRNhFayQXEWZygi74+9dAbQaGtwDODb6BaxbT/JEVRsB5pSYQR2Y+XuC/WcxRDQK eUYu5oWsjYkDuS8i1s7SqiVudrsTetPiXNoJn4YmDk4i73k/gpo+g5lBJkbnaESlEUS/ NM0mkiCJlT1mDeasuKiet4cPWxOFSia6CT8dyuZKmap+DdP+JZXRM0sm5zLC6eqwunzF 7YdJTgYvY8zbOjsJGeb+XkW4UqEuprmEf/mDJWTJqhuexXsLcav2nhiNcv7LZkggTAY8 AuUwvAo0YhPMQCR73IqKtzy1xTiXv2cAHWNyXQVFWEHty8dPaQIwISaTWisChbC2yx7W ubYw== X-Gm-Message-State: AAQBX9ceFek3nO5RRORqjFj1RmvuBA4B535u3oewWl/kHEV8dpF+/RKy O64LN8sKnlnxiCmqn7Wm+oMiCQ== X-Google-Smtp-Source: AKy350a+fQ5RH2pzme3FmdqfnV6Q9HMfXN8/2YLOzRVV6aO9E2YFNfCF27d33yNs3+ss0MWXL38FXg== X-Received: by 2002:a05:6a20:269f:b0:f0:7b8:c77b with SMTP id h31-20020a056a20269f00b000f007b8c77bmr14185926pze.59.1682358578033; Mon, 24 Apr 2023 10:49:38 -0700 (PDT) Received: from ziepe.ca ([206.223.160.26]) by smtp.gmail.com with ESMTPSA id b6-20020a63d806000000b005143d3fa0e0sm6814788pgh.2.2023.04.24.10.49.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Apr 2023 10:49:37 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1pr0Jj-001Vpp-HL; Mon, 24 Apr 2023 14:49:35 -0300 Date: Mon, 24 Apr 2023 14:49:35 -0300 From: Jason Gunthorpe To: Lorenzo Stoakes Cc: Dave Chinner , 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 Subject: Re: [PATCH] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: References: <20230423222941.GR447837@dread.disaster.area> <14c6f0f3-0747-4800-8718-4f109f7321ea@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14c6f0f3-0747-4800-8718-4f109f7321ea@lucifer.local> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sun, Apr 23, 2023 at 11:56:48PM +0100, Lorenzo Stoakes wrote: > This warned upon check should in reality not occur, because it implies the > GUP user is trying to do something broken and is _not_ explicitly telling > GUP that it knows it's doing it and can live with the consequences. And on > that basis, is worthy of a warning so we know we have to go put this flag > in that place (and know it is a source of problematic GUP usage), or fix > the caller. It is fine for debugging, but we can't merge user triggerable WARN_ONs.. Since the GUP caller has no idea if userspace might be maliciously passing in a file VMA we can't throw warnings. Jason