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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E9E0C433F5 for ; Wed, 8 Dec 2021 17:36:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C418F6B0071; Wed, 8 Dec 2021 12:35:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BF1C76B0073; Wed, 8 Dec 2021 12:35:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A922C6B0074; Wed, 8 Dec 2021 12:35:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0071.hostedemail.com [216.40.44.71]) by kanga.kvack.org (Postfix) with ESMTP id 96F396B0071 for ; Wed, 8 Dec 2021 12:35:52 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 608C07BE4B for ; Wed, 8 Dec 2021 17:35:42 +0000 (UTC) X-FDA: 78895329324.02.F40CB2E Received: from mail-ed1-f52.google.com (mail-ed1-f52.google.com [209.85.208.52]) by imf01.hostedemail.com (Postfix) with ESMTP id 1E94940002 for ; Wed, 8 Dec 2021 17:35:41 +0000 (UTC) Received: by mail-ed1-f52.google.com with SMTP id y13so10779950edd.13 for ; Wed, 08 Dec 2021 09:35:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+Ckibsje4Fnd3VY4SP1aED1W0LwwcbRPFpcYTanTTjQ=; b=enTUXU/e68+ySvnKJb/1GHyj4UVaV7OmU+vMxb/UK4v+JppxeTCBTukW3Xl7q+pd93 XEwYEcchfKiFKmmzAgmXDudTVKUpUgL4Nm2/EozStJQ/7z6Rnw3WtBEsIH3rXytLa8ag FBmrkAhHTJJtcP0SQb7fzFD50hNhpaBo4WssVoYDJ02np4SGajxqv0jUNt9pjNpkx9PO /V57V/cG0Qq2A1t5ksgJAtjCchc/v2qRybRN8ikKgW73/vaZOhJrtobKUoAgzFwk/Ffp SWwIYOR0BhQapaV4f+YnSliF5YFYxbRmZhGrrKswP2vKFzzg3vvZ2dNorKvIvnOayALL urJQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+Ckibsje4Fnd3VY4SP1aED1W0LwwcbRPFpcYTanTTjQ=; b=jlAZ501/8tc2z59XnV4aZadFrnK/CjgQjqbIAXa/Ig7n6iB+KOGn/2iX4TwgxzaawO JPEj4pXghy9eytCtSWe5C3xqkWDowinrLcLkVGvD5yHO7QK4KkLq64Vyhhc5aryBv8Oy CSVQbxJBohbJSJhLQKAPFmZAQrNiatxOo3TnkVxgFTeB4eJK24orwr+sh9F+MtKUq+wt PoJWh5muVc1sPbcDIkHUY9x4a1NdnBtLYoOzCx+EuaBYTuNQxyl1Qc9U2kzJA5wf6iu+ zMIjnqghiaI9vq6maFc7sjIzUP366cnj12ysXRLm6/X2CTfXg6Fjm++iKa40kNrO23Bd BjSQ== X-Gm-Message-State: AOAM531TyC7w7IcJHIqyJ3+/IRdI3qzHDZdZMnEOa4zNqsIQCikXIXyN SgnZKX9CtV/TLkcGalQ2aqAPVsQqDVJv8BRYpG+U7w== X-Google-Smtp-Source: ABdhPJxDn+3oG2kajdaXYIT7+4MrjY5A2Tbh/5sjaO7xfTGiXHZv73W078zOwbCjUIuzDoViD65s1US3GEIGqaBK13U= X-Received: by 2002:a17:906:2cd5:: with SMTP id r21mr9218020ejr.435.1638984939594; Wed, 08 Dec 2021 09:35:39 -0800 (PST) MIME-Version: 1.0 References: <20211204182314.1470076-1-pasha.tatashin@soleen.com> <20211204182314.1470076-4-pasha.tatashin@soleen.com> <20211207160508.6ef48f273c1ae14c0d02c6ac@linux-foundation.org> In-Reply-To: <20211207160508.6ef48f273c1ae14c0d02c6ac@linux-foundation.org> From: Pasha Tatashin Date: Wed, 8 Dec 2021 12:35:02 -0500 Message-ID: Subject: Re: [PATCH v2 3/4] mm: page table check To: Andrew Morton Cc: LKML , linux-mm , Linux Doc Mailing List , David Rientjes , Paul Turner , weixugc@google.com, Greg Thelen , Ingo Molnar , Jonathan Corbet , Will Deacon , Mike Rapoport , Kees Cook , Thomas Gleixner , Peter Zijlstra , masahiroy@kernel.org, Sami Tolvanen , Dave Hansen , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , frederic@kernel.org, "H. Peter Anvin" , "Aneesh Kumar K.V" , Jiri Slaby , Muchun Song , Fusion Future Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 1E94940002 X-Stat-Signature: dmh791wfp8cbn9fq683mmxibt5zjo4op Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b="enTUXU/e"; spf=pass (imf01.hostedemail.com: domain of pasha.tatashin@soleen.com designates 209.85.208.52 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=none X-HE-Tag: 1638984941-78912 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, Dec 7, 2021 at 7:05 PM Andrew Morton wrote: > > On Sat, 4 Dec 2021 18:23:13 +0000 Pasha Tatashin wrote: > > > Check user page table entries at the time they are added and removed. > > > > Allows to synchronously catch memory corruption issues related to double > > mapping. > > > > When a pte for an anonymous page is added into page table, we verify that > > this pte does not already point to a file backed page, and vice versa if > > this is a file backed page that is being added we verify that this page > > does not have an anonymous mapping > > > > We also enforce that read-only sharing for anonymous pages is allowed > > (i.e. cow after fork). All other sharing must be for file pages. > > > > Page table check allows to protect and debug cases where "struct page" > > metadata became corrupted for some reason. For example, when refcnt or > > mapcount become invalid. > > > > ... > > > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -1307,6 +1307,9 @@ config HAVE_ARCH_PFN_VALID > > config ARCH_SUPPORTS_DEBUG_PAGEALLOC > > bool > > > > +config ARCH_SUPPORTS_PAGE_TABLE_CHECK > > + bool > > + > > I guess a dependency on CONFIG_DEBUG_VM would be appropriate? I do not think CONFIG_DEBUG_VM is needed here. We would like to have page table check enabled on some production machines to ensure there are no double mappings. With CONFIG_DEBUG_VM enabled that would not be possible. For example, CONFIG_PAGE_OWNER, also uses extended struct page entries and does not depend on CONFIG_DEBUG_VM Pasha