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[156.151.31.86]) by mx.google.com with ESMTPS id l191si2035460pgd.549.2019.04.18.07.35.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2019 07:35:26 -0700 (PDT) Received-SPF: pass (google.com: domain of khalid.aziz@oracle.com designates 156.151.31.86 as permitted sender) client-ip=156.151.31.86; Authentication-Results: mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2018-07-02 header.b=ylFkenx2; spf=pass (google.com: domain of khalid.aziz@oracle.com designates 156.151.31.86 as permitted sender) smtp.mailfrom=khalid.aziz@oracle.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=oracle.com Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3IEJJ4K081960; Thu, 18 Apr 2019 14:34:46 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=AL/6XEs1B3BsG/bXzvFYIzuqptan4i6pMcE1H0+0SkI=; b=ylFkenx2gLgBHYyGmWupVhKcQN67lFFgacw3sDWrvc2UyMrlPdQyvRWc1MWjFkNik5jm 71B1aOguPFfyKZwocNP/SMGZxoxt7Fxi3QtN/SgpOhysgr/4HrVfbPeGtFHnwA3yIxlG Hy1hSEdxdOjsGvN/N6787w1ybzWXCK8WaBatHX4fFVDIF903zPvWinjxuorByNB7ibEF PNJoPTEBbn4WH+etQKqD4MGBh97w5FikjrdsLQhlVIen2uh7aIMHYexHO8Nf1B3EvtnK Lyg6v4V14wXFCheokSGz5j4y4rdfNOYyvGEP+ZwCp4EZo65ljg2Txcaea91uWAoku77x ag== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by userp2130.oracle.com with ESMTP id 2rvwk41a9g-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 18 Apr 2019 14:34:46 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3IEYHYK012588; Thu, 18 Apr 2019 14:34:45 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 2rwe7b0mb3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 18 Apr 2019 14:34:45 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x3IEYZET027844; Thu, 18 Apr 2019 14:34:35 GMT Received: from [192.168.1.16] (/24.9.64.241) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 18 Apr 2019 07:34:35 -0700 Subject: Re: [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO) To: Kees Cook , Andy Lutomirski Cc: Linus Torvalds , Thomas Gleixner , Nadav Amit , Ingo Molnar , Juerg Haefliger , Tycho Andersen , Julian Stecklina , Konrad Rzeszutek Wilk , Juerg Haefliger , deepa.srinivasan@oracle.com, chris hyser , Tyler Hicks , David Woodhouse , Andrew Cooper , Jon Masters , Boris Ostrovsky , iommu , X86 ML , "linux-alpha@vger.kernel.org" , "open list:DOCUMENTATION" , Linux List Kernel Mailing , Linux-MM , LSM List , Khalid Aziz , Andrew Morton , Peter Zijlstra , Dave Hansen , Borislav Petkov , "H. Peter Anvin" , Arjan van de Ven , Greg Kroah-Hartman References: <20190417161042.GA43453@gmail.com> <20190417170918.GA68678@gmail.com> <56A175F6-E5DA-4BBD-B244-53B786F27B7F@gmail.com> <20190417172632.GA95485@gmail.com> <063753CC-5D83-4789-B594-019048DE22D9@gmail.com> From: Khalid Aziz Organization: Oracle Corp Message-ID: <8f9d059d-e720-cd24-faa6-45493fc012e0@oracle.com> Date: Thu, 18 Apr 2019 08:34:32 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9231 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904180098 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9231 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904180098 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 4/17/19 11:41 PM, Kees Cook wrote: > On Wed, Apr 17, 2019 at 11:41 PM Andy Lutomirski wrot= e: >> I don't think this type of NX goof was ever the argument for XPFO. >> The main argument I've heard is that a malicious user program writes a= >> ROP payload into user memory (regular anonymous user memory) and then >> gets the kernel to erroneously set RSP (*not* RIP) to point there. >=20 > Well, more than just ROP. Any of the various attack primitives. The NX > stuff is about moving RIP: SMEP-bypassing. But there is still basic > SMAP-bypassing for putting a malicious structure in userspace and > having the kernel access it via the linear mapping, etc. >=20 >> I find this argument fairly weak for a couple reasons. First, if >> we're worried about this, let's do in-kernel CFI, not XPFO, to >=20 > CFI is getting much closer. Getting the kernel happy under Clang, LTO, > and CFI is under active development. (It's functional for arm64 > already, and pieces have been getting upstreamed.) >=20 CFI theoretically offers protection with fairly low overhead. I have not played much with CFI in clang. I agree with Linus that probability of bugs in XPFO implementation itself is a cause of concern. If CFI in Clang can provide us the same level of protection as XPFO does, I wouldn't want to push for an expensive change like XPFO. If Clang/CFI can't get us there for extended period of time, does it make sense to continue to poke at XPFO? Thanks, Khalid