From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D22D52F26 for ; Mon, 7 Feb 2022 19:10:11 +0000 (UTC) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 217Ih10O022971; Mon, 7 Feb 2022 19:09:41 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=dyalkAeyKfjg5aHVd6mQRDQDqmWJOUBGs31kbZ3xnMM=; b=XrtWCGa/awBKqiBsbGguRhzFJToZ/S9qxgv9tspsv9dQ1A3oTgwnh0Sm5APDP2+G/6Ea X1bITEatT5H12jAc0i7qzp3CStUafiWQNd8ekLMC0cVhMXtBUIDHfiUv1dypCvAYKZlo FjESWl2LqDxiea9CAV9ovGgzR7FBn2LvGZJWG1PCEOWDZ5zYneaMvxLGSIK2xqbHgDos osRzUE1kwOTprZ6azRE0stdftcW1we3WX8bbRYGHdSAF3GTox8Dr4U+jTEjMg2KR/zve cfw+N2TPcuQykGbNmHS2GF+E237+2aJqSJWqP/dQT6WRt3R0AIAkstmgFETwqIF5OCjE Sg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 3e22whhfrf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 07 Feb 2022 19:09:41 +0000 Received: from m0098413.ppops.net (m0098413.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 217IrMIw020670; Mon, 7 Feb 2022 19:09:40 GMT Received: from ppma04wdc.us.ibm.com (1a.90.2fa9.ip4.static.sl-reverse.com [169.47.144.26]) by mx0b-001b2d01.pphosted.com with ESMTP id 3e22whhfr4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 07 Feb 2022 19:09:40 +0000 Received: from pps.filterd (ppma04wdc.us.ibm.com [127.0.0.1]) by ppma04wdc.us.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 217J7TCe002298; Mon, 7 Feb 2022 19:09:39 GMT Received: from b03cxnp08026.gho.boulder.ibm.com (b03cxnp08026.gho.boulder.ibm.com [9.17.130.18]) by ppma04wdc.us.ibm.com with ESMTP id 3e2bt9qrfe-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 07 Feb 2022 19:09:39 +0000 Received: from b03ledav001.gho.boulder.ibm.com (b03ledav001.gho.boulder.ibm.com [9.17.130.232]) by b03cxnp08026.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 217J9cqi31588632 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 7 Feb 2022 19:09:38 GMT Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0D37F6E058; Mon, 7 Feb 2022 19:09:38 +0000 (GMT) Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 52ED86E059; Mon, 7 Feb 2022 19:09:30 +0000 (GMT) Received: from [9.65.240.79] (unknown [9.65.240.79]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 7 Feb 2022 19:09:30 +0000 (GMT) Message-ID: Date: Mon, 7 Feb 2022 21:09:28 +0200 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.5.1 Subject: Re: [PATCH v9 42/43] virt: sevguest: Add support to derive key Content-Language: en-US To: Brijesh Singh , Borislav Petkov Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Tobin Feldman-Fitzthum , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , "Dr . David Alan Gilbert" , brijesh.ksingh@gmail.com, tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com, Liam Merwick , Dov Murik References: <20220128171804.569796-1-brijesh.singh@amd.com> <20220128171804.569796-43-brijesh.singh@amd.com> <1cb4fdf5-7c1e-6c8f-1db6-8c976d6437c2@amd.com> From: Dov Murik In-Reply-To: <1cb4fdf5-7c1e-6c8f-1db6-8c976d6437c2@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: lLM5b9KPIZBForkzNm7IOXi0hUj_4zqC X-Proofpoint-ORIG-GUID: PVCYRX9sBn7puUs3---zr3p73u8apODq X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-02-07_06,2022-02-07_02,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 mlxlogscore=999 clxscore=1011 priorityscore=1501 bulkscore=0 spamscore=0 adultscore=0 mlxscore=0 phishscore=0 suspectscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202070115 On 07/02/2022 18:23, Brijesh Singh wrote: > > > On 2/7/22 2:52 AM, Borislav Petkov wrote: >> Those are allocated on stack, why are you clearing them? > > Yep, no need to explicitly clear it. I'll take it out in next rev. > Wait, this is key material generated by PSP and passed to userspace. Why leave copies of it floating around kernel memory? I thought that's the whole reason for these memzero_explicit() calls (maybe add a comment?). As an example, in arch/x86/crypto/aesni-intel_glue.c there are two calls to memzero_explicit(), both on stack variables; the only reason for these calls (as I understand it) is to avoid some future possible leak of this sensitive data (keys, cipher context, etc.). I'm sure there are other examples in the kernel code. -Dov