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authorMaxim Levitsky <mlevitsk@redhat.com>2021-07-19 16:05:00 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-08-18 08:57:04 +0200
commita17f2f2c89494c0974529579f3552ecbd1bc2d52 (patch)
treee481e08a2f3a7f517ad53e3ed8726438bf3e7939
parent7c1c96ffb658fbfe66c5ebed6bcb5909837bc267 (diff)
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KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656)
commit c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc upstream. 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: 89c8a4984fc9 ("KVM: SVM: Enable Virtual VMLOAD VMSAVE feature") Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kvm/svm.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 07a52f1bebe0..425444d08071 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -516,6 +516,9 @@ static void recalc_intercepts(struct vcpu_svm *svm)
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)