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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E317BC32771 for ; Mon, 26 Sep 2022 08:27:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229561AbiIZI1F (ORCPT ); Mon, 26 Sep 2022 04:27:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234222AbiIZI1A (ORCPT ); Mon, 26 Sep 2022 04:27:00 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F50A356CC for ; Mon, 26 Sep 2022 01:26:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1664180816; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=R6kVQxgDaKttefr6LvFpoSU7rbEztqe/rwJtDt7FFSw=; b=CxcrShJa9OtBOqYSENX6oI2I21oxbf+hVV7DMwJGnIgT9ClkLSpEVy8zIeOBQebABAhNWV TM4H3xWEjI30kuO7ZQiYDvarDx8gp2vhjoL9Q4LM5ENfOTUn6/pBvAYvjPu6O7G9AqqmnV P7Y2jrUsuvNLsoif08bq2O6yaKucC7Q= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-662-aHyvJQMnOL-SJGD_ZQ1zvA-1; Mon, 26 Sep 2022 04:26:55 -0400 X-MC-Unique: aHyvJQMnOL-SJGD_ZQ1zvA-1 Received: by mail-wm1-f71.google.com with SMTP id t14-20020a1c770e000000b003b4856a6ecaso1595033wmi.2 for ; Mon, 26 Sep 2022 01:26:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:organization:from:references :to:content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date; bh=R6kVQxgDaKttefr6LvFpoSU7rbEztqe/rwJtDt7FFSw=; b=ZVe6EnLz7o+A21tCoOkJc6oD5YeK+z++naZwa1N0AOz4CFrKJHNgMat+GXADBlAQPL rkA8GaXYMcf7TAP683dBLLSzfohE0xq74wbw+izCcIiFMI9vYMRBx/RYUuj5DvbNBiov foKtzwZzBTw/mSJBL2q55tKDKAb1/C/EgDWncewCWz+hLGd7t1xlinoUGA+CogkO8aP0 i3JtZbNodlOMPU8tp+dCvTycn8EkTeIQ1XMJrqus9Gw4jya/hiwjvJZca2mfDXIOkMCw /u/HKS2LJI3OTJR/NN8l4ss7sHN+x+5IrXCbEkFp1SFeyPTncuC1LlREKDJnVl3zu6tp l5cQ== X-Gm-Message-State: ACrzQf2PEd62esGnW51jVHuNG0VyPVyp+KY+M2W+3m5N9qLhGgdHo7FA 4D7lz49+xdDzt/sH+J4bzb+1acnEy2ggGffqwR27ZnHk2R8wdcOYmCHoy/jA0k2R3g6+Iq4BLqY HMeCOW6X+lZn2YcbrwEZrDDyY X-Received: by 2002:a05:600c:4f82:b0:3b4:9f2f:430b with SMTP id n2-20020a05600c4f8200b003b49f2f430bmr21036105wmq.16.1664180814431; Mon, 26 Sep 2022 01:26:54 -0700 (PDT) X-Google-Smtp-Source: AMsMyM7UbvwgXNhwxU1xdrO2alWyD+qqM4PoM2/a/0ZUOs6VVeKnKiIpHoohUPQxs97J8FJ848nRoQ== X-Received: by 2002:a05:600c:4f82:b0:3b4:9f2f:430b with SMTP id n2-20020a05600c4f8200b003b49f2f430bmr21036087wmq.16.1664180814116; Mon, 26 Sep 2022 01:26:54 -0700 (PDT) Received: from ?IPV6:2003:cb:c703:4b00:e090:7fa6:b7d6:d4a7? (p200300cbc7034b00e0907fa6b7d6d4a7.dip0.t-ipconnect.de. [2003:cb:c703:4b00:e090:7fa6:b7d6:d4a7]) by smtp.gmail.com with ESMTPSA id x2-20020a5d6b42000000b00225307f43fbsm13780433wrw.44.2022.09.26.01.26.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Sep 2022 01:26:53 -0700 (PDT) Message-ID: <353188b6-1fa6-0d53-b699-869a0588ee39@redhat.com> Date: Mon, 26 Sep 2022 10:26:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [PATCH 1/3] mm/page_table_check: Check writable zero page in page table check Content-Language: en-US To: Pasha Tatashin , akpm@linux-foundation.org, corbet@lwn.net, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rick.p.edgecombe@intel.com References: <20220911095923.3614387-1-pasha.tatashin@soleen.com> <20220911095923.3614387-2-pasha.tatashin@soleen.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220911095923.3614387-2-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11.09.22 11:59, Pasha Tatashin wrote: > From: Rick Edgecombe > > The zero page should remain all zero, so that it can be mapped as > read-only for read faults of memory that should be zeroed. If it is ever > mapped writable to userspace, it could become non-zero and so other apps > would unexpectedly get non-zero data. So the zero page should never be > mapped writable to userspace. Check for this condition in > page_table_check_set(). > > Signed-off-by: Rick Edgecombe > Signed-off-by: Pasha Tatashin > --- > mm/page_table_check.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/page_table_check.c b/mm/page_table_check.c > index e2062748791a..665ece0d55d4 100644 > --- a/mm/page_table_check.c > +++ b/mm/page_table_check.c > @@ -102,6 +102,8 @@ static void page_table_check_set(struct mm_struct *mm, unsigned long addr, > if (!pfn_valid(pfn)) > return; > > + BUG_ON(is_zero_pfn(pfn) && rw); We most probably don't want that: https://lkml.kernel.org/r/20220923113426.52871-2-david@redhat.com -- Thanks, David / dhildenb