From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 9 Mar 2026 11:40:52 +0000 (+0100)
Subject: KVM: SVM: check validity of VMCB controls when returning from SMM
X-Git-Tag: v7.0-rc4~4^2~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=be5fa8737d42c5ba16d2ea72c23681f8abbb07e8;p=thirdparty%2Flinux.git

KVM: SVM: check validity of VMCB controls when returning from SMM

The VMCB12 is stored in guest memory and can be mangled while in SMM; it
is then reloaded by svm_leave_smm(), but it is not checked again for
validity.

Move the cached vmcb12 control and save consistency checks out of
svm_set_nested_state() and into a helper, and reuse it in
svm_leave_smm().

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 53ab6ce3cc26..b36c33255bed 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -418,6 +418,15 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu)
 	return __nested_vmcb_check_controls(vcpu, ctl);
 }
 
+int nested_svm_check_cached_vmcb12(struct kvm_vcpu *vcpu)
+{
+	if (!nested_vmcb_check_save(vcpu) ||
+	    !nested_vmcb_check_controls(vcpu))
+		return -EINVAL;
+
+	return 0;
+}
+
 /*
  * If a feature is not advertised to L1, clear the corresponding vmcb12
  * intercept.
@@ -1028,8 +1037,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 	nested_copy_vmcb_control_to_cache(svm, &vmcb12->control);
 	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
 
-	if (!nested_vmcb_check_save(vcpu) ||
-	    !nested_vmcb_check_controls(vcpu)) {
+	if (nested_svm_check_cached_vmcb12(vcpu) < 0) {
 		vmcb12->control.exit_code    = SVM_EXIT_ERR;
 		vmcb12->control.exit_info_1  = 0;
 		vmcb12->control.exit_info_2  = 0;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2772f22df7ed..4eb2c36b8ff2 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4880,6 +4880,10 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 	vmcb12 = map.hva;
 	nested_copy_vmcb_control_to_cache(svm, &vmcb12->control);
 	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
+
+	if (nested_svm_check_cached_vmcb12(vcpu) < 0)
+		goto unmap_save;
+
 	ret = enter_svm_guest_mode(vcpu, smram64->svm_guest_vmcb_gpa, vmcb12, false);
 
 	if (ret)
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index ebd7b36b1ceb..6942e6b0eda6 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -797,6 +797,7 @@ static inline int nested_svm_simple_vmexit(struct vcpu_svm *svm, u32 exit_code)
 
 int nested_svm_exit_handled(struct vcpu_svm *svm);
 int nested_svm_check_permissions(struct kvm_vcpu *vcpu);
+int nested_svm_check_cached_vmcb12(struct kvm_vcpu *vcpu);
 int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
 			       bool has_error_code, u32 error_code);
 int nested_svm_exit_special(struct vcpu_svm *svm);