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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by MWH0EPF000A6734.mail.protection.outlook.com (10.167.249.26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.7611.14 via Frontend Transport; Mon, 20 May 2024 23:02:40 +0000 Received: from localhost (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Mon, 20 May 2024 18:02:39 -0500 From: Michael Roth To: CC: , , , , , Subject: [PATCH v2] KVM: SEV: Fix guest memory leak when handling guest requests Date: Mon, 20 May 2024 18:02:00 -0500 Message-ID: <20240520230200.1161826-1-michael.roth@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240518150457.1033295-1-michael.roth@amd.com> References: <20240518150457.1033295-1-michael.roth@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000A6734:EE_|DM4PR12MB6037:EE_ X-MS-Office365-Filtering-Correlation-Id: a4919ada-8640-47e2-172b-08dc7920f2fd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230031|36860700004|376005|1800799015|82310400017; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 May 2024 23:02:40.0792 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a4919ada-8640-47e2-172b-08dc7920f2fd X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000A6734.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6037 Before forwarding guest requests to firmware, KVM takes a reference on the 2 pages the guest uses for its request/response buffers. Make sure to release these when cleaning up after the request is completed. Also modify the logic to fail immediately (rather than report failure to the guest) if there is an error returning the guest pages to their expected state after the firmware command completes. Continue to propagate firmware errors to the guest as per the GHCB spec, however. Suggested-by: Sean Christopherson #for error-handling Signed-off-by: Michael Roth --- v2: - Fail to userspace if reclaim fails rather than trying to inform the guest of the error (Sean) - Remove the setup/cleanup helpers so that the cleanup logic is easier to follow (Sean) - Full original patch with this and other pending fix squashed in: https://github.com/mdroth/linux/commit/b4f51e38da22a2b163c546cb2a3aefd04446b3c7 arch/x86/kvm/svm/sev.c | 105 ++++++++++++++++++----------------------- 1 file changed, 47 insertions(+), 58 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 252bf7564f4b..446f9811cdaf 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3919,11 +3919,16 @@ static int sev_snp_ap_creation(struct vcpu_svm *svm) return ret; } -static int snp_setup_guest_buf(struct kvm *kvm, struct sev_data_snp_guest_request *data, - gpa_t req_gpa, gpa_t resp_gpa) +static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa) { - struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + struct sev_data_snp_guest_request data = {0}; + struct kvm *kvm = svm->vcpu.kvm; kvm_pfn_t req_pfn, resp_pfn; + sev_ret_code fw_err = 0; + int ret; + + if (!sev_snp_guest(kvm)) + return -EINVAL; if (!PAGE_ALIGNED(req_gpa) || !PAGE_ALIGNED(resp_gpa)) return -EINVAL; @@ -3933,64 +3938,49 @@ static int snp_setup_guest_buf(struct kvm *kvm, struct sev_data_snp_guest_reques return -EINVAL; resp_pfn = gfn_to_pfn(kvm, gpa_to_gfn(resp_gpa)); - if (is_error_noslot_pfn(resp_pfn)) - return -EINVAL; - - if (rmp_make_private(resp_pfn, 0, PG_LEVEL_4K, 0, true)) - return -EINVAL; - - data->gctx_paddr = __psp_pa(sev->snp_context); - data->req_paddr = __sme_set(req_pfn << PAGE_SHIFT); - data->res_paddr = __sme_set(resp_pfn << PAGE_SHIFT); - - return 0; -} - -static int snp_cleanup_guest_buf(struct sev_data_snp_guest_request *data) -{ - u64 pfn = __sme_clr(data->res_paddr) >> PAGE_SHIFT; - - if (snp_page_reclaim(pfn) || rmp_make_shared(pfn, PG_LEVEL_4K)) - return -EINVAL; - - return 0; -} - -static int __snp_handle_guest_req(struct kvm *kvm, gpa_t req_gpa, gpa_t resp_gpa, - sev_ret_code *fw_err) -{ - struct sev_data_snp_guest_request data = {0}; - int ret; - - if (!sev_snp_guest(kvm)) - return -EINVAL; - - ret = snp_setup_guest_buf(kvm, &data, req_gpa, resp_gpa); - if (ret) - return ret; + if (is_error_noslot_pfn(resp_pfn)) { + ret = -EINVAL; + goto release_req; + } - ret = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, fw_err); - if (ret) - return ret; + if (rmp_make_private(resp_pfn, 0, PG_LEVEL_4K, 0, true)) { + ret = -EINVAL; + kvm_release_pfn_clean(resp_pfn); + goto release_req; + } - ret = snp_cleanup_guest_buf(&data); - if (ret) - return ret; + data.gctx_paddr = __psp_pa(to_kvm_sev_info(kvm)->snp_context); + data.req_paddr = __sme_set(req_pfn << PAGE_SHIFT); + data.res_paddr = __sme_set(resp_pfn << PAGE_SHIFT); - return 0; -} + ret = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &fw_err); -static void snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa) -{ - struct kvm_vcpu *vcpu = &svm->vcpu; - struct kvm *kvm = vcpu->kvm; - sev_ret_code fw_err = 0; - int vmm_ret = 0; - - if (__snp_handle_guest_req(kvm, req_gpa, resp_gpa, &fw_err)) - vmm_ret = SNP_GUEST_VMM_ERR_GENERIC; + /* + * If the pages can't be placed back in the expected state then it is + * more reliable to always report the error to userspace than to try to + * let the guest deal with it somehow. Either way, the guest would + * likely terminate itself soon after a guest request failure anyway. + */ + if (snp_page_reclaim(resp_pfn) || + host_rmp_make_shared(resp_pfn, PG_LEVEL_4K)) { + ret = -EIO; + goto release_req; + } - ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SNP_GUEST_ERR(vmm_ret, fw_err)); + /* + * Unlike with reclaim failures, firmware failures should be + * communicated back to the guest via SW_EXITINFO2 rather than be + * treated as immediately fatal. + */ + ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, + SNP_GUEST_ERR(ret ? SNP_GUEST_VMM_ERR_GENERIC : 0, + fw_err)); + ret = 1; /* resume guest */ + kvm_release_pfn_dirty(resp_pfn); + +release_req: + kvm_release_pfn_clean(req_pfn); + return ret; } static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm) @@ -4268,8 +4258,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu) ret = 1; break; case SVM_VMGEXIT_GUEST_REQUEST: - snp_handle_guest_req(svm, control->exit_info_1, control->exit_info_2); - ret = 1; + ret = snp_handle_guest_req(svm, control->exit_info_1, control->exit_info_2); break; case SVM_VMGEXIT_UNSUPPORTED_EVENT: vcpu_unimpl(vcpu, -- 2.25.1