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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 60D7DC636C9 for ; Tue, 20 Jul 2021 20:45:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B752610A7 for ; Tue, 20 Jul 2021 20:45:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229516AbhGTUEc (ORCPT ); Tue, 20 Jul 2021 16:04:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233242AbhGTT6q (ORCPT ); Tue, 20 Jul 2021 15:58:46 -0400 Received: from mail-wm1-x332.google.com (mail-wm1-x332.google.com [IPv6:2a00:1450:4864:20::332]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B6A44C061762 for ; Tue, 20 Jul 2021 13:39:22 -0700 (PDT) Received: by mail-wm1-x332.google.com with SMTP id a23-20020a05600c2257b0290236ec98bebaso290607wmm.1 for ; Tue, 20 Jul 2021 13:39:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=BsY+NKv/XZi+6q8ALHCEokwQlprML2szGEsHbP7dUDo=; b=im/y0024Xt7uIk9rdJ9nEf9Flwqy6RP+EMxki/pwkYCD4BQ6ByyJ0trjzJOu8uTZAe PTjTRs0CGUZ9SXGI021qmwbl+TTgYBY45hEgF3MKgeCvlopbdpAYpc0cVXonAWEL5LtO iedT8rcx+onhhCcPYYrNp7DxA0H/WYwqJLDwjnGe06CGoMfqFIZjuFJLMLaQD2Aur+Pw +klfZUsBQpxY9nKDrDwdJkNiG7VLCth/Iayf9tE09FDdOZx89jVgZxVVOpt7BolQZvl2 2jZ69uFEEZf+Ngptqn/W4cxpq2ODZk5FwMnmcwowDsHhf4gxNY7HmU+qFFS4NdILmdBo DFYw== 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=BsY+NKv/XZi+6q8ALHCEokwQlprML2szGEsHbP7dUDo=; b=YrMNk+APni9wTMj/NAxjBWi8HIVBQkHcnvvJ84EpRGeSoIToxtzNisnfwPgYvFLMfI Tw//PP67yp5CDHt0xAz5CXQexfAQ/XHMFhc/1dYnphU/kYTftRFdStmIMeazbdfofwRt 4aECK48/FSEbAcOCZuex4bQTB4T12T7sHaO3Drj9hMHXfjSgWLlFi9sdXWQt7vH8MG+F HJc98vR4/vmRYRuLYTqaiDLnd/bKcKzy3/xKfSQBRw7rrSnGxjU3tFHefJS0ZXQCfw7v 3sbYevAOQrd0kEjabuMKz/en+GUA+/0ZL/Tkma+0Kpm2IE6Yw8W0muy+XvSkbL1no6Z3 +liw== X-Gm-Message-State: AOAM530qDoDbCEyXHu+rQ7uY0UicwUQTwPLbJr/9Hy5qD2eAxqC+p6nT s/l5/C/tDcPY8thVzSV9dL+kIQxuPV57/prZFXgYTA== X-Google-Smtp-Source: ABdhPJyFRM+FJuP84u9RfB5JCpLF0nd1AqQLHes34ffj0vZDREJluGzPfvMQprHdnNcX/mCbnu6aOkxZmjNtDQ3SnZo= X-Received: by 2002:a7b:c5d2:: with SMTP id n18mr290768wmk.97.1626813561085; Tue, 20 Jul 2021 13:39:21 -0700 (PDT) MIME-Version: 1.0 References: <796cbb7-5a1c-1ba0-dde5-479aba8224f2@google.com> <20210720155657.499127-1-peterx@redhat.com> In-Reply-To: <20210720155657.499127-1-peterx@redhat.com> From: Hugh Dickins Date: Tue, 20 Jul 2021 13:38:53 -0700 Message-ID: Subject: Re: [PATCH stable 5.10.y 0/2] mm/thp: Fix uffd-wp with fork(); crash on pmd migration entry on fork To: Peter Xu Cc: stable , linux-kernel , linux-mm , Igor Raits , Hillf Danton , Axel Rasmussen , Andrew Morton Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 20, 2021 at 8:57 AM Peter Xu wrote: > > In summary, this series should be needed for 5.10/5.12/5.13. This is the 5.10.y > backport of the series. Patch 1 is a dependency of patch 2, while patch 2 > should be the real fix. > > There's a minor conflict on patch 2 when cherry pick due to not having the new > helper called page_needs_cow_for_dma(). It's also mentioned at the entry of > patch 2. > > This series should be able to fix a rare race that mentioned in thread: > > https://lore.kernel.org/linux-mm/796cbb7-5a1c-1ba0-dde5-479aba8224f2@google.com/ > > This fact wasn't discovered when the fix got proposed and merged, because the > fix was originally about uffd-wp and its fork event. However it turns out that > the problematic commit b569a1760782f3d is also causing crashing on fork() of > pmd migration entries which is even more severe than the original uffd-wp > problem. > > Stable kernels at least on 5.12.y has the crash reproduced, and it's possible > 5.13.y and 5.10.y could hit it due to having the problematic commit > b569a1760782f3d but lacking of the uffd-wp fix patch (8f34f1eac382, which is > also patch 2 of this series). > > The pmd entry crash problem was reported by Igor Raits and > debugged by Hugh Dickins . > > Please review, thanks. And these two for 5.10.y look good to me also: I'm glad you decided in the end to keep 5.10's support for uffd-wp-fork. The first is just a straight cherry-pick of 5fc7a5f6fd04bc18f309d9f979b32ef7d1d0a997, but as you noted above, 8f34f1eac3820fc2722e5159acceb22545b30b0d needed one line of fixup for that tree. Thank you Peter, Hugh > > Peter Xu (2): > mm/thp: simplify copying of huge zero page pmd when fork > mm/userfaultfd: fix uffd-wp special cases for fork() > > include/linux/huge_mm.h | 2 +- > include/linux/swapops.h | 2 ++ > mm/huge_memory.c | 36 +++++++++++++++++------------------- > mm/memory.c | 25 +++++++++++++------------ > 4 files changed, 33 insertions(+), 32 deletions(-) > > -- > 2.31.1 > >