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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 50FF9C433DB for ; Mon, 21 Dec 2020 20:27:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1AD99224D1 for ; Mon, 21 Dec 2020 20:27:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726204AbgLUU1X (ORCPT ); Mon, 21 Dec 2020 15:27:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725908AbgLUU1W (ORCPT ); Mon, 21 Dec 2020 15:27:22 -0500 Received: from mail-lf1-x133.google.com (mail-lf1-x133.google.com [IPv6:2a00:1450:4864:20::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 67ECBC0613D3 for ; Mon, 21 Dec 2020 12:26:42 -0800 (PST) Received: by mail-lf1-x133.google.com with SMTP id h22so17206434lfu.2 for ; Mon, 21 Dec 2020 12:26:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jpofkkkZ7q2cLabxVdnoR1KpfpHXn/gunfXeSPC5btE=; b=efJi2L/jwYZG7lsZ3QUyQ+qJRPOSZJVBiQPV+KYdbYTDhEtiTiZJDpg0XZofJH/vr5 mvNIAsdX5eAcIdvkl8jdEU5jTFWJ/AX+Txhwsgdbaf4PRt5Mq82tnOXK8TWv+g9m7y52 H+k0THZ5Fa1365neNcweicdbjh0OKXdZEByM4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jpofkkkZ7q2cLabxVdnoR1KpfpHXn/gunfXeSPC5btE=; b=m05oYQ3CKRYVxACqUOZEankE98sPgu/33jcJOIeQLpcZAY4Pf2z86oWVucZMFtgzkc xDRAsTJq+ITA9+2r/8ufY/15REsPd6RPlMFl+jWGo1UYe5EjnqbdlW05+BNETKKFljZz RfTjXMqoQ/kZdA1TaywMaNNWsJtqY5RsSPkSE+903gZLvvXiePoK3j/AJBYp57RJ96r+ Osq2BpFchAXcRpQ1R/cudFzgXh9bi0YZp53yt9Sr1Q/S1DILI3SXmNiUWK2+Femr64iN XKVHautXuDYyDtcSofU//Oyb4eJMC/NjJDpDRi70mZLONRJJG4gQc0vLhL9rHGXgvZzD 9W6A== X-Gm-Message-State: AOAM530xuDWEmWOMc+Xozosh8BhQbqaBNK6mEoAW5luPCvZOgiGr5HEl KaIwEF4hINGpfaPizyuFDsEl/QcQ1TuP5A== X-Google-Smtp-Source: ABdhPJwW3IJgQByRWfI8RdVJS8yV+VyR8BF0Rjic6hIGRTt9nyOKRrEiXStxwVLP3iLm2siOzeS9aA== X-Received: by 2002:a19:54c:: with SMTP id 73mr7830099lff.551.1608582400342; Mon, 21 Dec 2020 12:26:40 -0800 (PST) Received: from mail-lf1-f43.google.com (mail-lf1-f43.google.com. [209.85.167.43]) by smtp.gmail.com with ESMTPSA id c5sm2252077lfh.160.2020.12.21.12.26.38 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Dec 2020 12:26:39 -0800 (PST) Received: by mail-lf1-f43.google.com with SMTP id m25so26656564lfc.11 for ; Mon, 21 Dec 2020 12:26:38 -0800 (PST) X-Received: by 2002:a05:6512:789:: with SMTP id x9mr6960312lfr.487.1608582398544; Mon, 21 Dec 2020 12:26:38 -0800 (PST) MIME-Version: 1.0 References: <20201219043006.2206347-1-namit@vmware.com> <20201221172711.GE6640@xz-x1> <76B4F49B-ED61-47EA-9BE4-7F17A26B610D@gmail.com> <9E301C7C-882A-4E0F-8D6D-1170E792065A@gmail.com> In-Reply-To: <9E301C7C-882A-4E0F-8D6D-1170E792065A@gmail.com> From: Linus Torvalds Date: Mon, 21 Dec 2020 12:26:22 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect To: Nadav Amit Cc: Yu Zhao , Peter Xu , Andrea Arcangeli , linux-mm , lkml , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , stable , Minchan Kim , Andy Lutomirski , Will Deacon , Peter Zijlstra Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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