Commit c7dfa400 authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Paolo Bonzini
Browse files

KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656) 



If L1 disables VMLOAD/VMSAVE intercepts, and doesn't enable
Virtual VMLOAD/VMSAVE (currently not supported for the nested hypervisor),
then VMLOAD/VMSAVE must operate on the L1 physical memory, which is only
possible by making L0 intercept these instructions.

Failure to do so allowed the nested guest to run VMLOAD/VMSAVE unintercepted,
and thus read/write portions of the host physical memory.

Fixes: 89c8a498 ("KVM: SVM: Enable Virtual VMLOAD VMSAVE feature")

Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0f923e07

arch/x86/kvm/svm/nested.c

+3 −0
Original line number Diff line number Diff line
@@ -158,6 +158,9 @@ void recalc_intercepts(struct vcpu_svm *svm) 
	/* If SMI is not intercepted, ignore guest SMI intercept as well  */

	if (!intercept_smi)

		vmcb_clr_intercept(c, INTERCEPT_SMI);



	vmcb_set_intercept(c, INTERCEPT_VMLOAD);

	vmcb_set_intercept(c, INTERCEPT_VMSAVE);

}



static void copy_vmcb_control_area(struct vmcb_control_area *dst,