[SRU Bionic 1/1] KVM: nVMX: add missing consistency checks for CR0 and CR4

[Cengiz Can]

From: Paolo Bonzini <pbonzini at redhat.com>

commit 112e66017bff7f2837030f34c2bc19501e9212d5 upstream.

The effective values of the guest CR0 and CR4 registers may differ from
those included in the VMCS12.  In particular, disabling EPT forces
CR4.PAE=1 and disabling unrestricted guest mode forces CR0.PG=CR0.PE=1.

Therefore, checks on these bits cannot be delegated to the processor
and must be performed by KVM.

Reported-by: Reima ISHII <ishiir at g.ecc.u-tokyo.ac.jp>
Cc: stable at vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
[OP: drop CC() macro calls, as tracing is not implemented in 4.19]
[OP: adjust "return -EINVAL" -> "return 1" to match current return logic]
Signed-off-by: Ovidiu Panait <ovidiu.panait at windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
CVE-2023-28464
(cherry picked from commit 495adb06518bb10f50e1aa1a1dbd5daa47d118f2 linux-4.19.y)
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 arch/x86/kvm/vmx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 005295f63559..da1ed6d5c04d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11479,7 +11479,7 @@ static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 				  u32 *exit_qual)
 {
-	bool ia32e;
+	bool ia32e = !!(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE);
 
 	*exit_qual = ENTRY_FAIL_DEFAULT;
 
@@ -11493,6 +11493,13 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		return 1;
 	}
 
+	if ((vmcs12->guest_cr0 & (X86_CR0_PG | X86_CR0_PE)) == X86_CR0_PG)
+		return 1;
+
+	if ((ia32e && !(vmcs12->guest_cr4 & X86_CR4_PAE)) ||
+	    (ia32e && !(vmcs12->guest_cr0 & X86_CR0_PG)))
+		return 1;
+
 	/*
 	 * If the load IA32_EFER VM-entry control is 1, the following checks
 	 * are performed on the field for the IA32_EFER MSR:
@@ -11504,7 +11511,6 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	 */
 	if (to_vmx(vcpu)->nested.nested_run_pending &&
 	    (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER)) {
-		ia32e = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) != 0;
 		if (!kvm_valid_efer(vcpu, vmcs12->guest_ia32_efer) ||
 		    ia32e != !!(vmcs12->guest_ia32_efer & EFER_LMA) ||
 		    ((vmcs12->guest_cr0 & X86_CR0_PG) &&
-- 
2.37.2