[PATCH] KVM: Fix memory leak on VCPU creation error

[PATCH] KVM: Fix memory leak on VCPU creation error

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka@siemens.com>

If kvm_arch_vcpu_setup failed, we leaked the allocated VCPU structure so
far.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 virt/kvm/kvm_main.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5814645..57b173c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1609,18 +1609,18 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 
 	r = kvm_arch_vcpu_setup(vcpu);
 	if (r)
-		return r;
+		goto vcpu_destroy;
 
 	mutex_lock(&kvm->lock);
 	if (atomic_read(&kvm->online_vcpus) == KVM_MAX_VCPUS) {
 		r = -EINVAL;
-		goto vcpu_destroy;
+		goto unlock_vcpu_destroy;
 	}
 
 	kvm_for_each_vcpu(r, v, kvm)
 		if (v->vcpu_id == id) {
 			r = -EEXIST;
-			goto vcpu_destroy;
+			goto unlock_vcpu_destroy;
 		}
 
 	BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);
@@ -1630,7 +1630,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 	r = create_vcpu_fd(vcpu);
 	if (r < 0) {
 		kvm_put_kvm(kvm);
-		goto vcpu_destroy;
+		goto unlock_vcpu_destroy;
 	}
 
 	kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;
@@ -1644,8 +1644,9 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 	mutex_unlock(&kvm->lock);
 	return r;
 
-vcpu_destroy:
+unlock_vcpu_destroy:
 	mutex_unlock(&kvm->lock);
+vcpu_destroy:
 	kvm_arch_vcpu_destroy(vcpu);
 	return r;
 }
-- 
1.7.1

Re: [PATCH] KVM: Fix memory leak on VCPU creation error

[Avi Kivity]

On 04/13/2011 02:32 AM, Jan Kiszka wrote:
> From: Jan Kiszka<jan.kiszka@siemens.com>
>
> If kvm_arch_vcpu_setup failed, we leaked the allocated VCPU structure so
> far.

> @@ -1609,18 +1609,18 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
>
>   	r = kvm_arch_vcpu_setup(vcpu);
>   	if (r)
> -		return r;
> +		goto vcpu_destroy;
>

kvm_arch_vcpu_setup() (at least x86's) does a vcpu->free() on failure.  
I think the current code is correct (if confusing).

-- 
error compiling committee.c: too many arguments to function

[PATCH] KVM: Clean up error handling during VCPU creation

[Jan Kiszka]

On 2011-04-17 11:16, Avi Kivity wrote:
> On 04/13/2011 02:32 AM, Jan Kiszka wrote:
>> From: Jan Kiszka<jan.kiszka@siemens.com>
>>
>> If kvm_arch_vcpu_setup failed, we leaked the allocated VCPU structure so
>> far.
> 
>> @@ -1609,18 +1609,18 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm
>> *kvm, u32 id)
>>
>>       r = kvm_arch_vcpu_setup(vcpu);
>>       if (r)
>> -        return r;
>> +        goto vcpu_destroy;
>>
> 
> kvm_arch_vcpu_setup() (at least x86's) does a vcpu->free() on failure. 
> I think the current code is correct (if confusing).

Right. How about cleaning this inconsistency up? It looks like there is
no problem calling kvm_arch_vcpu_destroy even if kvm_arch_vcpu_setup
bailed out early.

Jan

------8<------

From: Jan Kiszka <jan.kiszka@siemens.com>

So far kvm_arch_vcpu_setup is responsible for freeing the vcpu struct if
it fails. Move this confusing resonsibility back into the hands of
kvm_vm_ioctl_create_vcpu. Only kvm_arch_vcpu_setup of x86 is affected,
all other archs cannot fail.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 arch/x86/kvm/x86.c  |    5 -----
 virt/kvm/kvm_main.c |   11 ++++++-----
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1d5a7f4..9826d5d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6002,12 +6002,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 	if (r == 0)
 		r = kvm_mmu_setup(vcpu);
 	vcpu_put(vcpu);
-	if (r < 0)
-		goto free_vcpu;
 
-	return 0;
-free_vcpu:
-	kvm_x86_ops->vcpu_free(vcpu);
 	return r;
 }
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5814645..57b173c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1609,18 +1609,18 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 
 	r = kvm_arch_vcpu_setup(vcpu);
 	if (r)
-		return r;
+		goto vcpu_destroy;
 
 	mutex_lock(&kvm->lock);
 	if (atomic_read(&kvm->online_vcpus) == KVM_MAX_VCPUS) {
 		r = -EINVAL;
-		goto vcpu_destroy;
+		goto unlock_vcpu_destroy;
 	}
 
 	kvm_for_each_vcpu(r, v, kvm)
 		if (v->vcpu_id == id) {
 			r = -EEXIST;
-			goto vcpu_destroy;
+			goto unlock_vcpu_destroy;
 		}
 
 	BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);
@@ -1630,7 +1630,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 	r = create_vcpu_fd(vcpu);
 	if (r < 0) {
 		kvm_put_kvm(kvm);
-		goto vcpu_destroy;
+		goto unlock_vcpu_destroy;
 	}
 
 	kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;
@@ -1644,8 +1644,9 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 	mutex_unlock(&kvm->lock);
 	return r;
 
-vcpu_destroy:
+unlock_vcpu_destroy:
 	mutex_unlock(&kvm->lock);
+vcpu_destroy:
 	kvm_arch_vcpu_destroy(vcpu);
 	return r;
 }
-- 
1.7.1