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=ham 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 E9EADC07E95 for ; Tue, 20 Jul 2021 20:32:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5806961004 for ; Tue, 20 Jul 2021 20:32:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5806961004 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BE2826B006C; Tue, 20 Jul 2021 16:32:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B93166B0070; Tue, 20 Jul 2021 16:32:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A33C36B0071; Tue, 20 Jul 2021 16:32:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0060.hostedemail.com [216.40.44.60]) by kanga.kvack.org (Postfix) with ESMTP id 736526B006C for ; Tue, 20 Jul 2021 16:32:51 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 5FCBB18425A61 for ; Tue, 20 Jul 2021 20:32:48 +0000 (UTC) X-FDA: 78384114816.02.75DB806 Received: from mail-wr1-f46.google.com (mail-wr1-f46.google.com [209.85.221.46]) by imf29.hostedemail.com (Postfix) with ESMTP id 1B1089001A8F for ; Tue, 20 Jul 2021 20:32:47 +0000 (UTC) Received: by mail-wr1-f46.google.com with SMTP id m2so27380054wrq.2 for ; Tue, 20 Jul 2021 13:32:47 -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=Y8pNa0CXym7F7152JoRftjipPL1X5FqrC3oZp+fhJPxRDBoOC/PEAM5UWuGjJSN8Bm Nbr+PJ4TYPs8pVviq6gJLjCn2lvH8jy3K9hbGJwPDH9bQKBbWVyvcBDRB93DrAVv9WI4 JEJVqdiA5hKkw2PkyjSWcIPDqgNVlzBx8A/kcYY1//u4YjFhDGZZMy3+Ly0CsJ/Ze+Bg Sf6g0e5baadrTKwvBdIUwK0yMnKzFYgmbT/z4XHHXO8dcm1ANJK/QbWHVG3gAOc3pTow Uk8a8lwzGljBpC67NGrgHNVSIYELiaFXYC7Bc98Dz85K3T31ZEAgoSjBCOUsHqWl52sG ioDA== X-Gm-Message-State: AOAM530JvsbXbHnqUJDAcXT2/gQJ1pDxdTjGHofDe8Jz0J7NbZZo1MlI nf5BpyIjoPg8yjH6FHnHKJN1/eElyXDcnGl5K3hKaw== 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" Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=Vqe0E33h; spf=pass (imf29.hostedemail.com: domain of hughd@google.com designates 209.85.221.46 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: qwtdzxpswc7fsgdygbz89s1nwbypiuhw X-Rspamd-Queue-Id: 1B1089001A8F X-Rspamd-Server: rspam01 X-HE-Tag: 1626813167-642417 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > >