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Commit 119d547c authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Sasha Levin
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KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656) 



[ upstream commit c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc ]

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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 11cad2a4

arch/x86/kvm/svm.c

+3 −0
Original line number Diff line number Diff line
@@ -513,6 +513,9 @@ 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)