[PATCH AUTOSEL 4.20 42/42] kvm: sev: Fail KVM_SEV_INIT if already initialized

[PATCH AUTOSEL 4.20 42/42] kvm: sev: Fail KVM_SEV_INIT if already initialized

[Sasha Levin]

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