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David Alan Gilbert" , tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH v8 36/40] x86/sev: Provide support for SNP guest request NAEs To: Borislav Petkov References: <20211210154332.11526-1-brijesh.singh@amd.com> <20211210154332.11526-37-brijesh.singh@amd.com> From: Brijesh Singh Message-ID: <87d4999a-14cc-5070-4f03-001dd5f1d2b1@amd.com> Date: Thu, 27 Jan 2022 11:02:13 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BL1PR13CA0378.namprd13.prod.outlook.com (2603:10b6:208:2c0::23) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 875508c0-c8ba-4b29-f45d-08d9e1b6c6e2 X-MS-TrafficTypeDiagnostic: BY5PR12MB4888:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8882; 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It says bit 32 will should be set on error. >> + >> + ret = sev_es_ghcb_hv_call(ghcb, true, NULL, exit_code, input->req_gpa, input->resp_gpa); > ^^^^^ > > That's ctxt which is accessed without a NULL check in > verify_exception_info(). > > Why aren't you allocating a ctxt on stack like the other callers do? Typically the sev_es_ghcb_hv_handler() is called from #VC handler, which provides the context structure. But in this and PSC case, the caller is not a #VC handler, so we don't have a context structure. But as you pointed, we could allocate context structure on the stack and pass it down so that verify_exception_info() does not cause a panic with NULL deference (when HV violates the spec and inject exception while handling this NAE). thanks