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

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Message-ID: <CAA03e5Ggh4gODFspxcXAU6WRe0aMCvkG794JpwvyBf6ERs_6dA@mail.gmail.com>
Date:   Fri, 20 Aug 2021 19:11:46 -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 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")

Reviewed-by: Marc Orr <marcorr@...gle.com>