From patchwork Mon Feb 7 15:54:19 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Levitsky X-Patchwork-Id: 12737580 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 E3A6CC3526E for ; Mon, 7 Feb 2022 16:05:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1392300AbiBGQEQ (ORCPT ); Mon, 7 Feb 2022 11:04:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1385423AbiBGPzU (ORCPT ); Mon, 7 Feb 2022 10:55:20 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 46E2EC0401D2 for ; Mon, 7 Feb 2022 07:55:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1644249319; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZWkaPZigKR8ZVYYpYKUmXEITXI5Ito7CWFDFszKolT0=; b=FoU8VjHyA+VSai7IIWulvkhJQjrpuuPMquS9VTYvhuUenzPoTfK4I6jigdXuoh3qz15aGv og9ZRJaErQA1JH5Voh+7ke904RmlWh5KMeg7KkyO+9mAKXBztt58y7TWsGnaS3s8Gw71s2 sAusFqEUzeFoDplWE0J8E/mMQsHWbFM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-663-UJZl6NgZNt-ieIzpmnWFHQ-1; Mon, 07 Feb 2022 10:55:16 -0500 X-MC-Unique: UJZl6NgZNt-ieIzpmnWFHQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 064471091DA2; Mon, 7 Feb 2022 15:55:13 +0000 (UTC) Received: from localhost.localdomain (unknown [10.40.192.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id 51F757DE38; Mon, 7 Feb 2022 15:55:05 +0000 (UTC) From: Maxim Levitsky To: kvm@vger.kernel.org Cc: Tony Luck , "Chang S. Bae" , Thomas Gleixner , Wanpeng Li , Ingo Molnar , Vitaly Kuznetsov , Pawan Gupta , Dave Hansen , Paolo Bonzini , linux-kernel@vger.kernel.org, Rodrigo Vivi , "H. Peter Anvin" , intel-gvt-dev@lists.freedesktop.org, Joonas Lahtinen , Joerg Roedel , Sean Christopherson , David Airlie , Zhi Wang , Brijesh Singh , Jim Mattson , x86@kernel.org, Daniel Vetter , Borislav Petkov , Zhenyu Wang , Kan Liang , Jani Nikula , Maxim Levitsky , stable@vger.kernel.org Subject: [PATCH RESEND 02/30] KVM: x86: nSVM: fix potential NULL derefernce on nested migration Date: Mon, 7 Feb 2022 17:54:19 +0200 Message-Id: <20220207155447.840194-3-mlevitsk@redhat.com> In-Reply-To: <20220207155447.840194-1-mlevitsk@redhat.com> References: <20220207155447.840194-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Turns out that due to review feedback and/or rebases I accidentally moved the call to nested_svm_load_cr3 to be too early, before the NPT is enabled, which is very wrong to do. KVM can't even access guest memory at that point as nested NPT is needed for that, and of course it won't initialize the walk_mmu, which is main issue the patch was addressing. Fix this for real. Fixes: 232f75d3b4b5 ("KVM: nSVM: call nested_svm_load_cr3 on nested state load") Cc: stable@vger.kernel.org Signed-off-by: Maxim Levitsky --- arch/x86/kvm/svm/nested.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 1218b5a342fc8..39d280e7e80ef 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1457,18 +1457,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, !__nested_vmcb_check_save(vcpu, &save_cached)) goto out_free; - /* - * While the nested guest CR3 is already checked and set by - * KVM_SET_SREGS, it was set when nested state was yet loaded, - * thus MMU might not be initialized correctly. - * Set it again to fix this. - */ - - ret = nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3, - nested_npt_enabled(svm), false); - if (WARN_ON_ONCE(ret)) - goto out_free; - /* * All checks done, we can enter guest mode. Userspace provides @@ -1494,6 +1482,20 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, svm_switch_vmcb(svm, &svm->nested.vmcb02); nested_vmcb02_prepare_control(svm); + + /* + * While the nested guest CR3 is already checked and set by + * KVM_SET_SREGS, it was set when nested state was yet loaded, + * thus MMU might not be initialized correctly. + * Set it again to fix this. + */ + + ret = nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3, + nested_npt_enabled(svm), false); + if (WARN_ON_ONCE(ret)) + goto out_free; + + kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu); ret = 0; out_free: