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[156.151.31.85]) by mx.google.com with ESMTPS id o19si13176759pgk.324.2019.04.22.12.31.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Apr 2019 12:31:55 -0700 (PDT) Received-SPF: pass (google.com: domain of khalid.aziz@oracle.com designates 156.151.31.85 as permitted sender) client-ip=156.151.31.85; Authentication-Results: mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2018-07-02 header.b=oLnlTenx; spf=pass (google.com: domain of khalid.aziz@oracle.com designates 156.151.31.85 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 (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3MJUDBB049863; Mon, 22 Apr 2019 19:30:53 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : from : to : cc : references : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=WH/Ljdr8TJUTrAi5oLGMpFDZ+oLv/QGAaimWLH/RF5Y=; b=oLnlTenxF7nnPodU74CKxVdtTdurZTHC2c+IYDHYu4ConBppy1DQR5ZRD2yjJFvZgGWr s4yQwwuUvTu9u+sFyoVUu0Ps8OuhhW0poWi1ZMLvaVC5TBbAF1wwcZr5XAReyOOTF+by uC0TnLDiZT5r3TKE6PPp1vUjAz4Kig9RayQOAPeSyneDjrd8g3giZqr3VY0DWHpHGibW +Tp8jlms4x1+K3jD0LKvfWig3toDL2oxHG0Gk75UGHP6ZXqvAC5kZivppkWtzcLz1h9X XEAwsf7cBrXzU2kQ/Ajn/P/r+v3zskWbTDpMTbY0n+hrjLQtUDBZ3bbfv/WSjVOTlFLG 6g== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 2ryv2q001q-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 22 Apr 2019 19:30:53 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3MJUfFP107047; Mon, 22 Apr 2019 19:30:52 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2s0dwdv8c5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 22 Apr 2019 19:30:52 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x3MJUjCf011034; Mon, 22 Apr 2019 19:30:46 GMT Received: from [192.168.1.16] (/24.9.64.241) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 22 Apr 2019 12:30:45 -0700 Subject: Re: [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO) From: Khalid Aziz To: Kees Cook , Andy Lutomirski , Linus Torvalds Cc: 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> <8f9d059d-e720-cd24-faa6-45493fc012e0@oracle.com> Organization: Oracle Corp Message-ID: <302e3d5b-d2fd-3c25-335b-466ba83035c5@oracle.com> Date: Mon, 22 Apr 2019 13:30:41 -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: <8f9d059d-e720-cd24-faa6-45493fc012e0@oracle.com> 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=9235 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-1904220147 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9235 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-1904220147 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 4/18/19 8:34 AM, Khalid Aziz wrote: > On 4/17/19 11:41 PM, Kees Cook wrote: >> On Wed, Apr 17, 2019 at 11:41 PM Andy Lutomirski wro= te: >>> 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. >> >> 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. >> >>> 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 >> >> 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 no= t > 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. >=20 > If Clang/CFI can't get us there for extended period of time, does it > make sense to continue to poke at XPFO? Any feedback on continued effort on XPFO? If it makes sense to have XPFO available as a solution for ret2dir issue in case Clang/CFI does not work out, I will continue to refine it. -- Khalid