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[SRU,Focal,v2,1/1] KVM: nVMX: add missing consistency checks for CR0 and CR4

Message ID 20230427132744.555509-3-cengiz.can@canonical.com
State New
Headers show
Series [SRU,Focal,v2,1/1] KVM: nVMX: add missing consistency checks for CR0 and CR4 | expand

Commit Message

Cengiz Can April 27, 2023, 1:27 p.m. UTC 
From: Paolo Bonzini <pbonzini@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@g.ecc.u-tokyo.ac.jp>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE-2023-30456
(cherry picked from commit 65e4c9a6d0c9a8c81ce75576869d46fff5d7964f linux-5.4.y)
Signed-off-by: Cengiz Can <cengiz.can@canonical.com>
---
 arch/x86/kvm/vmx/nested.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
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Patch

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 2551582f4cbd..eeba6a9d56a6 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2779,7 +2779,7 @@  static int nested_vmx_check_guest_state(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;
 
@@ -2796,6 +2796,13 @@  static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
 		return -EINVAL;
 	}
 
+	if (CC((vmcs12->guest_cr0 & (X86_CR0_PG | X86_CR0_PE)) == X86_CR0_PG))
+		return -EINVAL;
+
+	if (CC(ia32e && !(vmcs12->guest_cr4 & X86_CR4_PAE)) ||
+	    CC(ia32e && !(vmcs12->guest_cr0 & X86_CR0_PG)))
+		return -EINVAL;
+
 	/*
 	 * If the load IA32_EFER VM-entry control is 1, the following checks
 	 * are performed on the field for the IA32_EFER MSR:
@@ -2807,7 +2814,6 @@  static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
 	 */
 	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 (CC(!kvm_valid_efer(vcpu, vmcs12->guest_ia32_efer)) ||
 		    CC(ia32e != !!(vmcs12->guest_ia32_efer & EFER_LMA)) ||
 		    CC(((vmcs12->guest_cr0 & X86_CR0_PG) &&