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 BC90EC07E9D for ; Mon, 26 Sep 2022 08:26:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 285B48E002D; Mon, 26 Sep 2022 04:26:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 235EC8E0007; Mon, 26 Sep 2022 04:26:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0FD928E002D; Mon, 26 Sep 2022 04:26:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 00E0F8E0007 for ; Mon, 26 Sep 2022 04:26:57 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id BBD49A0491 for ; Mon, 26 Sep 2022 08:26:57 +0000 (UTC) X-FDA: 79953556074.23.330AFC4 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf16.hostedemail.com (Postfix) with ESMTP id 395AA180018 for ; Mon, 26 Sep 2022 08:26:57 +0000 (UTC) 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-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-615-EHXq5NoVMxStNx44HijmOw-1; Mon, 26 Sep 2022 04:26:55 -0400 X-MC-Unique: EHXq5NoVMxStNx44HijmOw-1 Received: by mail-wm1-f72.google.com with SMTP id p9-20020a05600c23c900b003b48dc0cef1so1597217wmb.1 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=euoSab47baLcMN+FuD4fmGEmd1U5EJd1hY484JjoHwC4kK/jr4QPugU4g+TPU20tlm bPCiUo40lu6Y08HzwZh6MvDDkpBOLToGr4JzWWRRKTyVVLNbpLYbGn+/SgA88dX/Nx/Y RNeoOuC0YU5p62ZA/c5m2Ff81Q0rJ/otoBR9NaQ65UGkBw0dA+NGipAFOu97ya6An+cd eGliutJmQyO+LLSs0Pf7An73R0wTxRXP2vPIIQhDtTtd/k2FwaP+1fOefCzKNkLr0ijA ob7fVBLKMmnFnRhslTl+6HVUO1eFYsx+/YXYTrLJgmU7QTCp8zoSDSz0wiuBccbPl63L Dz/A== X-Gm-Message-State: ACrzQf2EM6vjt5r3Y/uDtD+vYBUnKR0TWIsnmKdcGEs8os8eG8JthKWX EguMZhPmfG+OFpfWF7jkCFecEHRHp5G8O3Il3hH9bgG6qqeszNzSMgjdMGFrjTWCw+HrApkVLFZ Lim2VGoZxi1Q= X-Received: by 2002:a05:600c:4f82:b0:3b4:9f2f:430b with SMTP id n2-20020a05600c4f8200b003b49f2f430bmr21036101wmq.16.1664180814428; 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 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> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664180817; a=rsa-sha256; cv=none; b=hb41WQEZfHzySYVDB7hpfOQFlw9LCBsiHDUZbBtd/+XAYKpvXXz+Er4Zhz5uE9ySLW5NWf G4B/Nga4ZIZySqHyqOakAnlTYR8E1cJs7wURG4hpXRCPl0jt+l1f8PCQFW11pc63qT1Uwd RdFPz1uJgWV1yIbDSw5tr6fBaJrwV8E= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CxcrShJa; spf=pass (imf16.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664180817; h=from:from:sender: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:dkim-signature; bh=R6kVQxgDaKttefr6LvFpoSU7rbEztqe/rwJtDt7FFSw=; b=Palt4kHGmW+iM6xP2ODJ0kQg7YrWdM2qjRjR/dcy59qzkXdH2MjkeQEnCEA2ERyTLci+uW dgffW8J0vJiUhYXUClECpFKMlGgNRg2br8BwgBKjzbVbf3TaZOXigMvtuNBWxi7uuniir/ 4qmtGuMf7Tj4VwfkBM9Tu5vSwcR2ehk= X-Rspamd-Queue-Id: 395AA180018 X-Rspamd-Server: rspam07 X-Rspam-User: Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CxcrShJa; spf=pass (imf16.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Stat-Signature: tqddtmxidnnsi6r7hgr7aij64kkpebp1 X-HE-Tag: 1664180817-267567 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 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