Patch-mainline: v6.1-rc1

Git-commit: 1cac8d9f6bd25df3713103e44e2d9ca0c2e03c33

References: bsc#1206616

From: Sean Christopherson <seanjc@google.com>

Date: Tue, 30 Aug 2022 15:37:08 +0200

Subject: [PATCH] KVM: x86: Check for existing Hyper-V vCPU in

 kvm_hv_vcpu_init()

When potentially allocating/initializing the Hyper-V vCPU struct, check

for an existing instance in kvm_hv_vcpu_init() instead of requiring

callers to perform the check.  Relying on callers to do the check is

risky as it's all too easy for KVM to overwrite vcpu->arch.hyperv and

leak memory, and it adds additional burden on callers without much

benefit.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Wei Liu <wei.liu@kernel.org>

Link: https://lore.kernel.org/r/20220830133737.1539624-5-vkuznets@redhat.com

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Juergen Gross <jgross@suse.com>

---

 arch/x86/kvm/hyperv.c | 27 ++++++++++++---------------

 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c

index 611c349a08bf..8aadd31ed058 100644

--- a/arch/x86/kvm/hyperv.c

+++ b/arch/x86/kvm/hyperv.c

@@ -936,9 +936,12 @@ static void stimer_init(struct kvm_vcpu_hv_stimer *stimer, int timer_index)

 static int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)

 {

-	struct kvm_vcpu_hv *hv_vcpu;

+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);

 	int i;

+	if (hv_vcpu)

+		return 0;

+

 	hv_vcpu = kzalloc(sizeof(struct kvm_vcpu_hv), GFP_KERNEL_ACCOUNT);

 	if (!hv_vcpu)

 		return -ENOMEM;

@@ -962,11 +965,9 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)

 	struct kvm_vcpu_hv_synic *synic;

 	int r;

-	if (!to_hv_vcpu(vcpu)) {

-		r = kvm_hv_vcpu_init(vcpu);

-		if (r)

-			return r;

-	}

+	r = kvm_hv_vcpu_init(vcpu);

+	if (r)

+		return r;

 	synic = to_hv_synic(vcpu);

@@ -1660,10 +1661,8 @@ int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)

 	if (!host && !vcpu->arch.hyperv_enabled)

 		return 1;

-	if (!to_hv_vcpu(vcpu)) {

-		if (kvm_hv_vcpu_init(vcpu))

-			return 1;

-	}

+	if (kvm_hv_vcpu_init(vcpu))

+		return 1;

 	if (kvm_hv_msr_partition_wide(msr)) {

 		int r;

@@ -1683,10 +1682,8 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)

 	if (!host && !vcpu->arch.hyperv_enabled)

 		return 1;

-	if (!to_hv_vcpu(vcpu)) {

-		if (kvm_hv_vcpu_init(vcpu))

-			return 1;

-	}

+	if (kvm_hv_vcpu_init(vcpu))

+		return 1;

 	if (kvm_hv_msr_partition_wide(msr)) {

 		int r;

@@ -2000,7 +1997,7 @@ void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu)

 		return;

 	}

-	if (!to_hv_vcpu(vcpu) && kvm_hv_vcpu_init(vcpu))

+	if (kvm_hv_vcpu_init(vcpu))

 		return;

 	hv_vcpu = to_hv_vcpu(vcpu);

-- 

2.35.3