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Reply-To: Mingwei Zhang <mizhang@google.com>
Date:   Wed, 18 Aug 2021 05:39:05 +0000
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Subject: [PATCH v2 1/4] KVM: SVM: fix missing sev_decommission in sev_receive_start
From:   Mingwei Zhang <mizhang@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        John Allen <john.allen@amd.com>
Cc:     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@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>,
        Marc Orr <marcorr@google.com>, Peter Gonda <pgonda@google.com>,
        Vipin Sharma <vipinsh@google.com>,
        Mingwei Zhang <mizhang@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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