Subject: Re: [PATCH v2] KVM: VMX: Fix rflags cache during vCPU reset
To: Wanpeng Li <kernellwp@gmail.com>, Jim Mattson <jmattson@google.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Wanpeng Li <wanpeng.li@hotmail.com>, Nadav Amit <nadav.amit@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <049b65c8-63a2-4c67-b66f-3b063038e3f8@redhat.com>
Date: Tue, 5 Dec 2017 14:54:02 +0100
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On 05/12/2017 01:53, Wanpeng Li wrote:
>> That seems like a convoluted path to produce an illegal RFLAGS value.
>> What's to prevent syzkaller from simply clearing bit 1 of RFLAGS with
>> the KVM_SET_REGS ioctl?
> Yeah, it can happen. Which do you prefer, ioctl fails or |
> X86_EFLAGS_FIXED unconditionally in the ioctl handler in kvm?

I suspect somebody might be passing an all-zero regs struct to
KVM_SET_REGS, so ORing X86_EFLAGS_FIXED is better.

Thanks,

Paolo