From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8749329BD94 for ; Mon, 15 Dec 2025 19:28:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765826898; cv=none; b=KKdZjUCuwKZEfvULEvX4tnhajUwE+rwAQSqf3WU2IRos/05niA8JGHQBHsms0BDYPXqMKZUlS2G1F9P5fiyhlRZfyCRMfYXh08HdGrl9ZEYNsPOm9mn2wjGqWXrPOE9x3AdqKyQe1X4OTubsu4K2O5R/PYDLcWf1UTZBV0pCm/E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765826898; c=relaxed/simple; bh=h+iuLlFRcl6c9NLyEW1CdLyWZbKvYmk7h9fYlqoJNRQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sDoFTQWzHW+E2C6jPtCRcqg3CwBgbBTEd04Vy2GyljxDc1E/Lhhk9kXBUior9bdPjA0ZyFUHhM5pD931UI1e/FlVIFHUcw34PKsFJKgzfFx2P2lKbxqRgiJUG0no0GKV1orNddA79J9qrxeXaeUgeWlhrQRfIYBH8ZDkNwjeGRQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=uvaXVoN1; arc=none smtp.client-ip=91.218.175.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="uvaXVoN1" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1765826889; 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=QiGyeLhYElDyqRv1pQ6xp6qJfHPlEL9LQfOUQxzhz2M=; b=uvaXVoN1aKbMGGQZEHQhiYCZpvgKdrVfakhrX47A9GrxEvcZMRQ2rTSBew55xfdju8XCBd mLkQZrYz5lESHKG8raa55whw/vP1IxfMxp6ESPjZRKgJi4xU1uAzRZ+VNXxWYuYywdZOGJ e3YlEOY98rarXR0PDNEyeN6RqEKIk/U= From: Yosry Ahmed To: Paolo Bonzini , Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed , stable@vger.kernel.org Subject: [PATCH v3 05/26] KVM: nSVM: Triple fault if mapping VMCB12 fails on nested #VMEXIT Date: Mon, 15 Dec 2025 19:27:00 +0000 Message-ID: <20251215192722.3654335-7-yosry.ahmed@linux.dev> In-Reply-To: <20251215192722.3654335-1-yosry.ahmed@linux.dev> References: <20251215192722.3654335-1-yosry.ahmed@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT KVM currently injects a #GP and hopes for the best if mapping VMCB12 fails on nested #VMEXIT, and only if the failure mode is -EINVAL. Mapping the VMCB12 could also fail if creating host mappings fails. After the #GP is injected, nested_svm_vmexit() bails early, without cleaning up (e.g. KVM_REQ_GET_NESTED_STATE_PAGES is set, is_guest_mode() is true, etc). Move mapping VMCB12 a bit later, after leaving guest mode and clearing KVM_REQ_GET_NESTED_STATE_PAGES, right before the VMCB12 is actually used. Instead of optionally injecting a #GP, triple fault the guest if mapping VMCB12 fails since KVM cannot make a sane recovery. The APM states that a #VMEXIT will triple fault if host state is illegal or an exception occurs while loading host state, so the behavior is not entirely made up. Also update the WARN_ON() in svm_get_nested_state_pages() to WARN_ON_ONCE() to avoid future user-triggeable bugs spamming kernel logs and potentially causing issues. Fixes: cf74a78b229d ("KVM: SVM: Add VMEXIT handler and intercepts") CC: stable@vger.kernel.org Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Signed-off-by: Yosry Ahmed --- arch/x86/kvm/svm/nested.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index a5a367fd8bb1..e6b87ae46783 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1078,24 +1078,14 @@ void svm_copy_vmloadsave_state(struct vmcb *to_vmcb, struct vmcb *from_vmcb) int nested_svm_vmexit(struct vcpu_svm *svm) { struct kvm_vcpu *vcpu = &svm->vcpu; + gpa_t vmcb12_gpa = svm->nested.vmcb12_gpa; struct vmcb *vmcb01 = svm->vmcb01.ptr; struct vmcb *vmcb02 = svm->nested.vmcb02.ptr; struct vmcb *vmcb12; struct kvm_host_map map; - int rc; - - rc = kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.vmcb12_gpa), &map); - if (rc) { - if (rc == -EINVAL) - kvm_inject_gp(vcpu, 0); - return 1; - } - - vmcb12 = map.hva; /* Exit Guest-Mode */ leave_guest_mode(vcpu); - svm->nested.vmcb12_gpa = 0; WARN_ON_ONCE(svm->nested.nested_run_pending); kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu); @@ -1103,8 +1093,16 @@ int nested_svm_vmexit(struct vcpu_svm *svm) /* in case we halted in L2 */ kvm_set_mp_state(vcpu, KVM_MP_STATE_RUNNABLE); + svm->nested.vmcb12_gpa = 0; + + if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcb12_gpa), &map)) { + kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu); + return 1; + } + /* Give the current vmcb to the guest */ + vmcb12 = map.hva; vmcb12->save.es = vmcb02->save.es; vmcb12->save.cs = vmcb02->save.cs; vmcb12->save.ss = vmcb02->save.ss; @@ -1259,8 +1257,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm) nested_svm_uninit_mmu_context(vcpu); - rc = nested_svm_load_cr3(vcpu, vmcb01->save.cr3, false, true); - if (rc) + if (nested_svm_load_cr3(vcpu, vmcb01->save.cr3, false, true)) return 1; /* @@ -1893,7 +1890,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu) { - if (WARN_ON(!is_guest_mode(vcpu))) + if (WARN_ON_ONCE(!is_guest_mode(vcpu))) return true; if (!vcpu->arch.pdptrs_from_userspace && -- 2.52.0.239.gd5f0c6e74e-goog