linux-kernel - [PATCH] KVM: SVM: fix missing sev_decommission in sev_receive

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Message-Id: <20210912181815.3899316-1-mizhang@google.com>
Date:   Sun, 12 Sep 2021 18:18:15 +0000
From:   Mingwei Zhang <mizhang@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     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@...r.kernel.org,
        linux-kernel@...r.kernel.org, Alper Gun <alpergun@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Brijesh Singh <brijesh.singh@....com>,
        David Rienjes <rientjes@...gle.com>,
        Marc Orr <marcorr@...gle.com>, John Allen <john.allen@....com>,
        Peter Gonda <pgonda@...gle.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Vipin Sharma <vipinsh@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>
Subject: [PATCH] KVM: SVM: fix missing sev_decommission in sev_receive_start

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>

Reviewed-by: Marc Orr <marcorr@...gle.com>
Acked-by: Brijesh Singh <brijesh.singh@....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,
-- 
2.33.0.309.g3052b89438-goog