linux-kernel - Re: [PATCH] KVM: apic: avoid calculating pending eoi from an uninitialized val

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Date:   Fri, 21 Feb 2020 01:31:28 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH] KVM: apic: avoid calculating pending eoi from an
 uninitialized val

Vitaly Kuznetsov <vkuznets@...hat.com> writes:
>linmiaohe <linmiaohe@...wei.com> writes:
>> When get user eoi value failed, var val would be uninitialized and 
>> result in calculating pending eoi from an uninitialized val. 
>> Initialize var val to 0 to fix this case.
>
>Let me try to suggest an alternative wording,
>
>"When pv_eoi_get_user() fails, 'val' may remain uninitialized and the return value of pv_eoi_get_pending() becomes random. Fix the issue by initializing the variable."

Sounds much better. You're really good at it. :) Thanks.

>>
>>
>Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
>
>But why compilers don't complain?

Maybe it's because @val only remain uninitialized when pv_eoi_get_user() failed?