linux-kernel - Re: [PATCH v2 7/7] KVM: selftests: Test pmu event filter with incompatible kvm_pmu_event

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Date:   Thu, 25 May 2023 08:55:29 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Jinrong Liang <ljr.kernel@...il.com>
Cc:     Like Xu <like.xu.linux@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>,
        Aaron Lewis <aaronlewis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Jinrong Liang <cloudliang@...cent.com>,
        linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] KVM: selftests: Test pmu event filter with
 incompatible kvm_pmu_event_filter

On Thu, May 25, 2023, Jinrong Liang wrote:
> Sean Christopherson <seanjc@...gle.com> 于2023年5月25日周四 07:50写道：
> > > +static uint64_t test_incompatible_filter(struct kvm_vcpu *vcpu, uint32_t action,
> > > +                                      uint32_t bitmap)
> > > +{
> > > +     struct incompatible_pmu_event_filter err_f;
> > > +
> > > +     err_f.action = action;
> > > +     err_f.fixed_counter_bitmap = bitmap;
> > > +     ioctl((vcpu->vm)->fd, KVM_SET_PMU_EVENT_FILTER, &err_f.action);
> >
> > This is completely busted.  It "passes" by luck, not because it's a valid test.
> > The size of the argument is embedded in the IOCTL number itself, which means that
> > unless glibc is being very nice and using a macro + typeof + sizeof to sanity check
> > things, which I highly doubt is the case, this ioctl() is passing random stack data,
> > a.k.a. garbage, to KVM.
> >
> > In short, drop this patch.
> 
> Thank you for letting us know about the issues with the patch. I will
> drop the patch as suggested. Would you advise me to prepare version 3
> to remove this patch?

More comments on the other patches are incoming, please hold off on v3 until then.