From: Yosry Ahmed <yosry@kernel.org>
Date: Tue, 3 Mar 2026 00:34:09 +0000 (+0000)
Subject: KVM: nSVM: Add missing consistency check for nCR3 validity
X-Git-Tag: v7.1-rc1~118^2~4^2~39
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b71138fcc362c67ebe66747bb22cb4e6b4d6a651;p=thirdparty%2Flinux.git

KVM: nSVM: Add missing consistency check for nCR3 validity

From the APM Volume #2, 15.25.4 (24593—Rev. 3.42—March 2024):

  When VMRUN is executed with nested paging enabled (NP_ENABLE = 1), the
  following conditions are considered illegal state combinations, in
  addition to those mentioned in “Canonicalization and Consistency Checks”:
      • Any MBZ bit of nCR3 is set.
      • Any G_PAT.PA field has an unsupported type encoding or any
        reserved field in G_PAT has a nonzero value.

Add the consistency check for nCR3 being a legal GPA with no MBZ bits
set.  Note, the G_PAT.PA check is being handled separately[*].

Link: https://lore.kernel.org/kvm/20260205214326.1029278-3-jmattson@google.com [*]
Fixes: 4b16184c1cca ("KVM: SVM: Initialize Nested Nested MMU context on VMRUN")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-16-yosry@kernel.org
[sean: capture everything in CC(), massage changelog formatting]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 2ed6530e7bd1f..a59b976c16db9 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -348,6 +348,10 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 	if (CC(control->asid == 0))
 		return false;
 
+	if (CC((control->nested_ctl & SVM_NESTED_CTL_NP_ENABLE) &&
+	       !kvm_vcpu_is_legal_gpa(vcpu, control->nested_cr3)))
+		return false;
+
 	if (CC(!nested_svm_check_bitmap_pa(vcpu, control->msrpm_base_pa,
 					   MSRPM_SIZE)))
 		return false;