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 X-Spam-Level: X-Spam-Status: No, score=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,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 7B6D6C433E0 for ; Mon, 21 Dec 2020 21:25:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E98D22B43 for ; Mon, 21 Dec 2020 21:25:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726371AbgLUVZU (ORCPT ); Mon, 21 Dec 2020 16:25:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726101AbgLUVZU (ORCPT ); Mon, 21 Dec 2020 16:25:20 -0500 Received: from mail-il1-x12c.google.com (mail-il1-x12c.google.com [IPv6:2607:f8b0:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C58EBC0613D6 for ; Mon, 21 Dec 2020 13:24:39 -0800 (PST) Received: by mail-il1-x12c.google.com with SMTP id n9so10208134ili.0 for ; Mon, 21 Dec 2020 13:24:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=gt0GOM+mu9eCAi9ZwxTkAxhSO6qei0FrG7NI5v/BoDI=; b=ACpDdyiwt4yzErIqLdCpeaNIBrR4/bgLdfjMt1/9F8ZZFOMHGNH56+Edfr2m9edLS8 YJoTMl2xATIDPeDCMciiGgJDwtllCD0RR+tXlKRWRIR5DHsL67/Qwmes3l7G1WpZrOgO FmbDWZqJa+20i6x4NSrn35qd2TAUf06sM+fTT4kZ4yzPg2Ri3E/RGJRGYUHLazaLlgh0 Z6GfhQWEW9PuoSOR0RgQdp9JucsYj5Oxj6SQ9qj3B9e7jB0lW9pz6jCnm6gmiPNM8sN5 gAAUGlXFu7zyctRCrFwGHfnFgyBtXYb6kAsE3rukf71mRYJ/HBcRNBBRWloAU77Sywxg kcdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=gt0GOM+mu9eCAi9ZwxTkAxhSO6qei0FrG7NI5v/BoDI=; b=f0q1gTdWIz36MXbwzoB2Bce0IKJQsvf0c+P814z5ihW6gNmAFltqc3jweZLSKtzElh 8wVsSwa4JaHyg8X/LP07tR+ExBb/E1G0omLYOHXybDe3b4Nwto952u2VtgNTgtr9rolh nRVkzoLq/sjF7nmpSP01QfmndhjDmh5m7UPdH0z+w2QCQFNX5Km9jwgt/j8epOEzAlho 7WVWOTt1mZfFeuRtdfX0f5WvTDmIiyeYmz7dmD7u1BQcPOc8Sd7F1Rws6U9IssAS6SlP XTQA/KpavwSI6J8mYUKx6dhW9Ju5q1WlMe53BMjnsLk3mgOjk5h2l7EMuza0Ynq/+5hC PKbw== X-Gm-Message-State: AOAM531tmyMQBhjxEialR+Y3vyQQF3GBU48u4zVSn2r/vJzLBn8lp20t e1lQDtJhMDahCWTy2hmO3Et/Yw== X-Google-Smtp-Source: ABdhPJychXn0XslNMBwA9JjNdnXAOfUJzvSg3VkeXylKiLgYPfJfDi/cgzqACLTvDBwEhNJyinzdTg== X-Received: by 2002:a92:d8cc:: with SMTP id l12mr17823222ilo.64.1608585878937; Mon, 21 Dec 2020 13:24:38 -0800 (PST) Received: from google.com ([2620:15c:183:200:7220:84ff:fe09:2d90]) by smtp.gmail.com with ESMTPSA id t2sm14659937ili.31.2020.12.21.13.24.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Dec 2020 13:24:38 -0800 (PST) Date: Mon, 21 Dec 2020 14:24:34 -0700 From: Yu Zhao To: Linus Torvalds Cc: Nadav Amit , Peter Xu , Andrea Arcangeli , linux-mm , lkml , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , stable , Minchan Kim , Andy Lutomirski , Will Deacon , Peter Zijlstra Subject: Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect Message-ID: References: <20201221172711.GE6640@xz-x1> <76B4F49B-ED61-47EA-9BE4-7F17A26B610D@gmail.com> <9E301C7C-882A-4E0F-8D6D-1170E792065A@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 21, 2020 at 12:26:22PM -0800, Linus Torvalds wrote: > On Mon, Dec 21, 2020 at 12:23 PM Nadav Amit wrote: > > > > Using mmap_write_lock() was my initial fix and there was a strong pushback > > on this approach due to its potential impact on performance. > > From whom? > > Somebody who doesn't understand that correctness is more important > than performance? And that userfaultfd is not the most important part > of the system? > > The fact is, userfaultfd is CLEARLY BUGGY. > > Linus Fair enough. Nadav, for your patch (you might want to update the commit message). Reviewed-by: Yu Zhao While we are all here, there is also clear_soft_dirty() that could use a similar fix...