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 882BFC07E9B for ; Tue, 20 Jul 2021 20:45:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 64F2460FF3 for ; Tue, 20 Jul 2021 20:45:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231927AbhGTUDu (ORCPT ); Tue, 20 Jul 2021 16:03:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237639AbhGTTwL (ORCPT ); Tue, 20 Jul 2021 15:52:11 -0400 Received: from mail-wr1-x42c.google.com (mail-wr1-x42c.google.com [IPv6:2a00:1450:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58ACBC061574 for ; Tue, 20 Jul 2021 13:32:48 -0700 (PDT) Received: by mail-wr1-x42c.google.com with SMTP id r11so27330891wro.9 for ; Tue, 20 Jul 2021 13:32:48 -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=AIWk5BKdHIXkOStxfUF7zNtVWR8PXbbd7J5me9z4RZE=; b=Vqe0E33hZAiq5rO4tkECZ2RNv4SKNV35O5vhgqgSxDZC2zxfsszv1ni6QOvhafBAhQ npz0nXmOzv9H6qCSMYJXeGZEaWGPxyVknU+Ny47YyxAYZRrIYYapnWghw5ZKdmU0hnPu b7JUrDsrufoQAj7OCdJj0NCdxT60hWuVXucLgrFpdeFYZAdbOflFD1AH5lG+ihDVZ85v Od9dE0Ad7ifBl7PAJR4qyidOPaixtVTZTw5d4zCBZUJcd/X8vj65605ytoN2zH9Dkth6 YibwHVxdHRobRZrPKTNpK31Wr2qBW63WoJKhtQlgzcxHQDj1NfuDWADmODRDzqlIlHdc 65wg== 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=AIWk5BKdHIXkOStxfUF7zNtVWR8PXbbd7J5me9z4RZE=; b=iL1fW+lNRR35eCvFDjD28rxYANVjM7SuBtVD5O8RqWjNAvUYQkppUXx7i4NV479K4T pgDNMHOZuVLkB20fMgGHawF0f6XN6DnWsQvgWfkP6kJKh/WFiyRQjMQ5HPxx1OO7S076 5CCjKltr0XXFuspTn50guDFXoO/7Vt5VxppGBXOD3YUlt13DTRysk8YHbcLbrJ3CXLAI e7XVmvpx5NUSzTo14zgZbcinkPQFLhXl4Zt0Iem/9gMEE7mGJnRTsPQs5m+1xK0BUojP /FIm6ej9Z6Jm5ASM67qcKGoofH8S4saF1X95aT9mxp336voe7qzn/spw0Pu8Y7M1SH0U sCog== X-Gm-Message-State: AOAM5311akBoNFrUVjX4qbqwxJNKMKGWmNABTxdChLCkhFPIRUtwjXxq eSyCAnTV8RA9BpUsw8m8vX10wk3on/hWhNNyzEPv5g== X-Google-Smtp-Source: ABdhPJzrhB5zVHMUs5Co+5EcZK8Y4nLQ9oRLi9EZKRUaMJmk/QBvPOmssls+DKWeTB4xv4TAXpAMHJQKtwP0WDQ9b4Y= X-Received: by 2002:adf:ea8c:: with SMTP id s12mr39508206wrm.404.1626813166651; Tue, 20 Jul 2021 13:32:46 -0700 (PDT) MIME-Version: 1.0 References: <796cbb7-5a1c-1ba0-dde5-479aba8224f2@google.com> <20210720155150.497148-1-peterx@redhat.com> In-Reply-To: <20210720155150.497148-1-peterx@redhat.com> From: Hugh Dickins Date: Tue, 20 Jul 2021 13:32:19 -0700 Message-ID: Subject: Re: [PATCH stable 5.13.y/5.12.y 0/2] mm/thp: Fix uffd-wp with fork(); crash on pmd migration entry on fork To: Peter Xu Cc: stable , linux-mm , linux-kernel , Axel Rasmussen , Andrew Morton , Hillf Danton , Igor Raits 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 8:52 AM Peter Xu wrote: > > In summary: this series should be needed for 5.10/5.12/5.13. This is the > 5.13.y/5.12.y backport of the series, and it should be able to be applied on > both of the branches. Patch 1 is a dependency of patch 2, while patch 2 should > be the real fix. > > 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. These two 5.13.y patches look just right to me, thank you Peter (and 5.12.19 announced EOL overnight, so nothing more wanted for that). But these do just amount to asking stable@vger.kernel.org to cherry-pick the two commits 5fc7a5f6fd04bc18f309d9f979b32ef7d1d0a997 8f34f1eac3820fc2722e5159acceb22545b30b0d Hugh (I'd usually reply with alpine rather than gmail, but I see extra blank lines on these 0/2s that way; but the patches themselves are good.) > > 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 > >