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.
This fixes CVE-2021-3656, which was discovered by Maxim Levitsky and
Paolo Bonzini.
Fixes: 89c8a4984fc9 ("KVM: SVM: Enable Virtual VMLOAD VMSAVE feature")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
CVE-2021-3656
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Ben Romer <benjamin.romer@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
c->intercept_dr = h->intercept_dr | g->intercept_dr;
c->intercept_exceptions = h->intercept_exceptions | g->intercept_exceptions;
c->intercept = h->intercept | g->intercept;
+
+ c->intercept |= (1ULL << INTERCEPT_VMLOAD);
+ c->intercept |= (1ULL << INTERCEPT_VMSAVE);
}
static inline struct vmcb *get_host_vmcb(struct vcpu_svm *svm)