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KVM: x86: Protect exit_reason from being used in Spectre-v1/L1TF attacks

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This fixes a Spectre-v1/L1TF vulnerability in vmx_handle_exit().
While exit_reason is set by the hardware and therefore should not be
attacker-influenced, an unknown exit_reason could potentially be used to
perform such an attack.

Fixes: 55d2375e58 ("KVM: nVMX: Move nested code to dedicated files")

Signed-off-by: Marios Pomonis <pomonis@google.com>
Signed-off-by: Nick Finco <nifi@google.com>
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marios Pomonis 2019-12-11 12:47:51 -08:00 committed by Paolo Bonzini
parent 125ffc5e0a
commit c926f2f723
1 changed files with 34 additions and 27 deletions
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19
arch/x86/kvm/vmx/vmx.c
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@ -5913,8 +5913,10 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
if (exit_fastpath == EXIT_FASTPATH_SKIP_EMUL_INS) {
kvm_skip_emulated_instruction(vcpu);
return 1;
} else if (exit_reason < kvm_vmx_max_exit_handlers
&& kvm_vmx_exit_handlers[exit_reason]) {
}
if (exit_reason >= kvm_vmx_max_exit_handlers)
goto unexpected_vmexit;
#ifdef CONFIG_RETPOLINE
if (exit_reason == EXIT_REASON_MSR_WRITE)
return kvm_emulate_wrmsr(vcpu);
@ -5929,10 +5931,16 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
else if (exit_reason == EXIT_REASON_EPT_MISCONFIG)
return handle_ept_misconfig(vcpu);
#endif
exit_reason = array_index_nospec(exit_reason,
kvm_vmx_max_exit_handlers);
if (!kvm_vmx_exit_handlers[exit_reason])
goto unexpected_vmexit;
return kvm_vmx_exit_handlers[exit_reason](vcpu);
} else {
vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",
exit_reason);
unexpected_vmexit:
vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason);
dump_vmcs();
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror =
@ -5941,7 +5949,6 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
vcpu->run->internal.data[0] = exit_reason;
return 0;
}
}
/*
* Software based L1D cache flush which is used when microcode providing