From patchwork Thu Nov 3 13:57:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Levitsky X-Patchwork-Id: 13030032 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C2D4C4332F for ; Thu, 3 Nov 2022 13:58:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231459AbiKCN6t (ORCPT ); Thu, 3 Nov 2022 09:58:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231144AbiKCN6p (ORCPT ); Thu, 3 Nov 2022 09:58:45 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E46E1402E for ; Thu, 3 Nov 2022 06:57:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667483864; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=fUsqybhXp/D82YuS/O33LZfOTzfFB038d5lKiyOEhC8=; b=JJHt7TaPaevjU3CwkgkvxwpGgCqwycXTzmshRJLSF17+VPVZ4NimTlE4z3B7U7n38VL2A+ aJ7KDlWqPmJc4ehH+vRohouldgf/v56QOLvdjq7NiCJDzDOVVCUfIPxGdwTx1NhSXFvWxv rcASehiB1iNWclMETplvf98npVxcrxw= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-528-wG8_w1AzN_-3brZ9aiF0Rw-1; Thu, 03 Nov 2022 09:57:41 -0400 X-MC-Unique: wG8_w1AzN_-3brZ9aiF0Rw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BD30A3815D2F; Thu, 3 Nov 2022 13:57:40 +0000 (UTC) Received: from amdlaptop.tlv.redhat.com (dhcp-4-238.tlv.redhat.com [10.35.4.238]) by smtp.corp.redhat.com (Postfix) with ESMTP id 52F8B40C2140; Thu, 3 Nov 2022 13:57:37 +0000 (UTC) From: Maxim Levitsky To: kvm@vger.kernel.org Cc: Paolo Bonzini , "H. Peter Anvin" , Shuah Khan , Yang Zhong , Wei Wang , Colton Lewis , Sean Christopherson , Jim Mattson , Chenyi Qiang , Borislav Petkov , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Dave Hansen , Ingo Molnar , David Matlack , Peter Xu , Maxim Levitsky , linux-kselftest@vger.kernel.org Subject: [PATCH 0/9] nSVM: Security and correctness fixes Date: Thu, 3 Nov 2022 15:57:27 +0200 Message-Id: <20221103135736.42295-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Recently while trying to fix some unit tests I found a CVE in SVM nested code. In 'shutdown_interception' vmexit handler we call kvm_vcpu_reset. However if running nested and L1 doesn't intercept shutdown, we will still end up running this function and trigger a bug in it. The bug is that this function resets the 'vcpu->arch.hflags' without properly leaving the nested state, which leaves the vCPU in inconsistent state, which later triggers a kernel panic in SVM code. The same bug can likely be triggered by sending INIT via local apic to a vCPU which runs a nested guest. On VMX we are lucky that the issue can't happen because VMX always intercepts triple faults, thus triple fault in L2 will always be redirected to L1. Plus the 'handle_triple_fault' of VMX doesn't reset the vCPU. INIT IPI can't happen on VMX either because INIT events are masked while in VMX mode. First 4 patches in this series address the above issue, and are already posted on the list with title, ('nSVM: fix L0 crash if L2 has shutdown condtion which L1 doesn't intercept') I addressed the review feedback and also added a unit test to hit this issue. In addition to these patches I noticed that KVM doesn't honour SHUTDOWN intercept bit of L1 on SVM, and I included a fix to do so - its only for correctness as a normal hypervisor should always intercept SHUTDOWN. A unit test on the other hand might want to not do so. I also extendted the triple_fault_test selftest to hit this issue. Finaly I found another security issue, I found a way to trigger a kernel non rate limited printk on SVM from the guest, and last patch in the series fixes that. A unit test I posted to kvm-unit-tests project hits this issue, so no selftest was added. Best regards, Maxim Levitsky Maxim Levitsky (9): KVM: x86: nSVM: leave nested mode on vCPU free KVM: x86: nSVM: harden svm_free_nested against freeing vmcb02 while still in use KVM: x86: add kvm_leave_nested KVM: x86: forcibly leave nested mode on vCPU reset KVM: selftests: move idt_entry to header kvm: selftests: add svm nested shutdown test KVM: x86: allow L1 to not intercept triple fault KVM: selftests: add svm part to triple_fault_test KVM: x86: remove exit_int_info warning in svm_handle_exit arch/x86/kvm/svm/nested.c | 12 +++- arch/x86/kvm/svm/svm.c | 10 +-- arch/x86/kvm/vmx/nested.c | 4 +- arch/x86/kvm/x86.c | 29 ++++++-- tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/include/x86_64/processor.h | 13 ++++ .../selftests/kvm/lib/x86_64/processor.c | 13 ---- .../kvm/x86_64/svm_nested_shutdown_test.c | 71 +++++++++++++++++++ .../kvm/x86_64/triple_fault_event_test.c | 71 ++++++++++++++----- 10 files changed, 174 insertions(+), 51 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86_64/svm_nested_shutdown_test.c