linux-kernel - Re: [PATCH] KVM: VMX: Set failure code in prepare

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Date:   Tue, 30 Nov 2021 17:30:12 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Oliver Upton <oupton@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Krish Sadhukhan <krish.sadhukhan@...cle.com>,
        Peter Shier <pshier@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] KVM: VMX: Set failure code in prepare_vmcs02()

On 11/30/21 13:53, Dan Carpenter wrote:
> The error paths in the prepare_vmcs02() function are supposed to set
> *entry_failure_code but this path does not.  It leads to using an
> uninitialized variable in the caller.
> 
> Fixes: 71f7347025bf ("KVM: nVMX: Load GUEST_IA32_PERF_GLOBAL_CTRL MSR on VM-Entry")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>   arch/x86/kvm/vmx/nested.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 315fa456d368..f321300883f9 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -2594,8 +2594,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>   
>   	if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) &&
>   	    WARN_ON_ONCE(kvm_set_msr(vcpu, MSR_CORE_PERF_GLOBAL_CTRL,
> -				     vmcs12->guest_ia32_perf_global_ctrl)))
> +				     vmcs12->guest_ia32_perf_global_ctrl))) {
> +		*entry_failure_code = ENTRY_FAIL_DEFAULT;
>   		return -EINVAL;
> +	}
>   
>   	kvm_rsp_write(vcpu, vmcs12->guest_rsp);
>   	kvm_rip_write(vcpu, vmcs12->guest_rip);
> 

Yeah, I suppose that's the right thing to do (though it really shouldn't 
happen because the value is checked earlier in 
nested_vmx_check_guest_state).

Queued, thanks.

Paolo