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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 X-Rspamd-Queue-Id: AA860160004 X-Rspam-User: nil Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b="XrtWCGa/"; dmarc=pass (policy=none) header.from=ibm.com; spf=pass (imf08.hostedemail.com: domain of dovmurik@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=dovmurik@linux.ibm.com X-Stat-Signature: 7baaocpcofd6ynaqpwx49ur7op5iafqc X-Rspamd-Server: rspam08 X-HE-Tag: 1644261006-631626 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 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