linux-kernel - Re: [PATCH] KVM: X86: init irq->level in kvm_pv_kick_cpu

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Message-ID: <cb2e6cb9-8e8b-209c-b81e-2e7ea894c55c@redhat.com>
Date:   Wed, 2 Aug 2017 10:14:25 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Longpeng(Mike)" <longpeng2@...wei.com>, rkrcmar@...hat.com
Cc:     tglx@...utronix.de, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, weidong.huang@...wei.com,
        arei.gonglei@...wei.com, wangxinxin.wang@...wei.com
Subject: Re: [PATCH] KVM: X86: init irq->level in kvm_pv_kick_cpu_op

On 02/08/2017 05:20, Longpeng(Mike) wrote:
> 'lapic_irq' is a local variable and its 'level' field isn't
> initialized, so 'level' is random, it doesn't matter but
> makes UBSAN unhappy:
> 
> UBSAN: Undefined behaviour in .../lapic.c:...
> load of value 10 is not a valid value for type '_Bool'
> ...
> Call Trace:
>  [<ffffffff81f030b6>] dump_stack+0x1e/0x20
>  [<ffffffff81f03173>] ubsan_epilogue+0x12/0x55
>  [<ffffffff81f03b96>] __ubsan_handle_load_invalid_value+0x118/0x162
>  [<ffffffffa1575173>] kvm_apic_set_irq+0xc3/0xf0 [kvm]
>  [<ffffffffa1575b20>] kvm_irq_delivery_to_apic_fast+0x450/0x910 [kvm]
>  [<ffffffffa15858ea>] kvm_irq_delivery_to_apic+0xfa/0x7a0 [kvm]
>  [<ffffffffa1517f4e>] kvm_emulate_hypercall+0x62e/0x760 [kvm]
>  [<ffffffffa113141a>] handle_vmcall+0x1a/0x30 [kvm_intel]
>  [<ffffffffa114e592>] vmx_handle_exit+0x7a2/0x1fa0 [kvm_intel]
> ...
> 
> Signed-off-by: Longpeng(Mike) <longpeng2@...wei.com>
> ---
>  arch/x86/kvm/x86.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6c97c82..b411f92 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6215,6 +6215,7 @@ static void kvm_pv_kick_cpu_op(struct kvm *kvm, unsigned long flags, int apicid)
>  
>  	lapic_irq.shorthand = 0;
>  	lapic_irq.dest_mode = 0;
> +	lapic_irq.level = 0;
>  	lapic_irq.dest_id = apicid;
>  	lapic_irq.msi_redir_hint = false;

Looks good.  Thanks,

Paolo