linux-kernel - Re: [PATCH v2 1/4] KVM: SVM: fix missing sev_decommission in sev_receive

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Date:   Fri, 20 Aug 2021 19:30:46 -0700
From:   Marc Orr <marcorr@...gle.com>
To:     Mingwei Zhang <mizhang@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        John Allen <john.allen@....com>,
        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>, kvm list <kvm@...r.kernel.org>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alper Gun <alpergun@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        David Rienjes <rientjes@...gle.com>,
        Peter Gonda <pgonda@...gle.com>,
        Vipin Sharma <vipinsh@...gle.com>
Subject: Re: [PATCH v2 1/4] KVM: SVM: fix missing sev_decommission in sev_receive_start

On Fri, Aug 20, 2021 at 7:11 PM Marc Orr <marcorr@...gle.com> wrote:
>
> On Tue, Aug 17, 2021 at 10:39 PM Mingwei Zhang <mizhang@...gle.com> wrote:
> >
> > sev_decommission is needed in the error path of sev_bind_asid. The purpose
> > of this function is to clear the firmware context. Missing this step may
> > cause subsequent SEV launch failures.
> >
> > Although missing sev_decommission issue has previously been found and was
> > fixed in sev_launch_start function. It is supposed to be fixed on all
> > scenarios where a firmware context needs to be freed. According to the AMD
> > SEV API v0.24 Section 1.3.3:
> >
> > "The RECEIVE_START command is the only command other than the LAUNCH_START
> > command that generates a new guest context and guest handle."
> >
> > The above indicates that RECEIVE_START command also requires calling
> > sev_decommission if ASID binding fails after RECEIVE_START succeeds.
> >
> > So add the sev_decommission function in sev_receive_start.
> >
> > Cc: Alper Gun <alpergun@...gle.com>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: Brijesh Singh <brijesh.singh@....com>
> > Cc: David Rienjes <rientjes@...gle.com>
> > Cc: Marc Orr <marcorr@...gle.com>
> > Cc: John Allen <john.allen@....com>
> > Cc: Peter Gonda <pgonda@...gle.com>
> > Cc: Sean Christopherson <seanjc@...gle.com>
> > Cc: Tom Lendacky <thomas.lendacky@....com>
> > Cc: Vipin Sharma <vipinsh@...gle.com>
> >
> > Fixes: af43cbbf954b ("KVM: SVM: Add support for KVM_SEV_RECEIVE_START command")
> > Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> > ---
> >  arch/x86/kvm/svm/sev.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index 75e0b21ad07c..55d8b9c933c3 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -1397,8 +1397,10 @@ static int sev_receive_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> >
> >         /* Bind ASID to this guest */
> >         ret = sev_bind_asid(kvm, start.handle, error);
> > -       if (ret)
> > +       if (ret) {
> > +               sev_decommission(start.handle);
> >                 goto e_free_session;
> > +       }
> >
> >         params.handle = start.handle;
> >         if (copy_to_user((void __user *)(uintptr_t)argp->data,
> > --
> > 2.33.0.rc1.237.g0d66db33f3-goog
>
> Should this patch have the following Fixes tag?
>
> Fixes: af43cbbf954b ("KVM: SVM: Add support for KVM_SEV_RECEIVE_START command")

Oops. I missed that it already has the Fixes tag. Please ignore this comment.