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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     David Rientjes <rientjes@google.com>,
        =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,
        Sasha Levin <sashal@kernel.org>, kvm@vger.kernel.org
Subject: [PATCH AUTOSEL 4.20 42/42] kvm: sev: Fail KVM_SEV_INIT if already initialized
Date:   Sat,  9 Feb 2019 13:47:34 -0500
Message-Id: <20190209184734.125935-42-sashal@kernel.org>
In-Reply-To: <20190209184734.125935-1-sashal@kernel.org>
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From: David Rientjes <rientjes@google.com>

[ Upstream commit 3f14a89d1132dcae3c8ce6721c6ef51f6e6d9b5f ]

By code inspection, it was found that multiple calls to KVM_SEV_INIT
could deplete asid bits and overwrite kvm_sev_info's regions_list.

Multiple calls to KVM_SVM_INIT is not likely to occur with QEMU, but this
should likely be fixed anyway.

This code is serialized by kvm->lock.

Fixes: 1654efcbc431 ("KVM: SVM: Add KVM_SEV_INIT command")
Reported-by: Cfir Cohen <cfir@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 101f53ccf571..3db60e0a59fd 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6248,6 +6248,9 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	int asid, ret;
 
 	ret = -EBUSY;
+	if (unlikely(sev->active))
+		return ret;
+
 	asid = sev_asid_new();
 	if (asid < 0)
 		return ret;
-- 
2.19.1