Re: [PATCH v2 1/4] KVM: SVM: fix missing sev_decommission in sev_receive_start

From: Marc Orr <marcorr@google.com>
To: Mingwei Zhang <mizhang@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	John Allen <john.allen@amd.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm list <kvm@vger.kernel.org>,
	linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
	Alper Gun <alpergun@google.com>, Borislav Petkov <bp@alien8.de>,
	David Rienjes <rientjes@google.com>,
	Peter Gonda <pgonda@google.com>,
	Vipin Sharma <vipinsh@google.com>
Subject: Re: [PATCH v2 1/4] KVM: SVM: fix missing sev_decommission in sev_receive_start
Date: Fri, 20 Aug 2021 19:11:46 -0700	[thread overview]
Message-ID: <CAA03e5Ggh4gODFspxcXAU6WRe0aMCvkG794JpwvyBf6ERs_6dA@mail.gmail.com> (raw)
In-Reply-To: <20210818053908.1907051-2-mizhang@google.com>

On Tue, Aug 17, 2021 at 10:39 PM Mingwei Zhang <mizhang@google.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@google.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: David Rienjes <rientjes@google.com>
> Cc: Marc Orr <marcorr@google.com>
> Cc: John Allen <john.allen@amd.com>
> Cc: Peter Gonda <pgonda@google.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Vipin Sharma <vipinsh@google.com>
>
> Fixes: af43cbbf954b ("KVM: SVM: Add support for KVM_SEV_RECEIVE_START command")
> Signed-off-by: Mingwei Zhang <mizhang@google.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@google.com>