KVM: nVMX: avoid NULL pointer dereference with incorrect EVMCS GPAs
commit 95fa10103d
upstream.
When an EVMCS enabled L1 guest on KVM will tries doing enlightened VMEnter
with EVMCS GPA = 0 the host crashes because the
evmcs_gpa != vmx->nested.hv_evmcs_vmptr
condition in nested_vmx_handle_enlightened_vmptrld() will evaluate to
false (as nested.hv_evmcs_vmptr is zeroed after init). The crash will
happen on vmx->nested.hv_evmcs pointer dereference.
Another problematic EVMCS ptr value is '-1' but it only causes host crash
after nested_release_evmcs() invocation. The problem is exactly the same as
with '0', we mistakenly think that the EVMCS pointer hasn't changed and
thus nested.hv_evmcs_vmptr is valid.
Resolve the issue by adding an additional !vmx->nested.hv_evmcs
check to nested_vmx_handle_enlightened_vmptrld(), this way we will
always be trying kvm_vcpu_map() when nested.hv_evmcs is NULL
and this is supposed to catch all invalid EVMCS GPAs.
Also, initialize hv_evmcs_vmptr to '0' in nested_release_evmcs()
to be consistent with initialization where we don't currently
set hv_evmcs_vmptr to '-1'.
Cc: stable@vger.kernel.org
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
parent
84c6ce00e2
commit
4873041d37
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@ -223,7 +223,7 @@ static inline void nested_release_evmcs(struct kvm_vcpu *vcpu)
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return;
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kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map, true);
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vmx->nested.hv_evmcs_vmptr = -1ull;
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vmx->nested.hv_evmcs_vmptr = 0;
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vmx->nested.hv_evmcs = NULL;
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}
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@ -1828,7 +1828,8 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
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if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa))
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return 1;
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if (unlikely(evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
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if (unlikely(!vmx->nested.hv_evmcs ||
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evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
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if (!vmx->nested.hv_evmcs)
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vmx->nested.current_vmptr = -1ull;
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