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KVM: Fix memory leak on VCPU creation error

PATCH In review Jan Kiszka 2 participants 3 messages Apr 12, 2011 – Apr 17, 2011

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x86 KVM KVM x86
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Jan Kiszka

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#0 lore raw

PATCH 1/1 KVM: Fix memory leak on VCPU creation error

From: Jan Kiszka <[email protected]>

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

Signed-off-by Jan Kiszka <[email protected]>
---
 virt/kvm/kvm_main.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)
virt/kvm/kvm_main.c +6 -5
index 5814645..57b173c 100644
@@ -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;
 }
Signature · 1 line
1.7.1
#1 lore raw

virt/kvm/kvm_main.c static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) · line 1613

Quoted 12 lines · Jan Kiszka

From: Jan Kiszka<[email protected]>

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

virt/kvm/kvm_main.c +1 -1
@@ -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).

Signature · 1 line
error compiling committee.c: too many arguments to function
author
#2 lore raw

PATCH 1/1 KVM: Clean up error handling during VCPU creation

Quoted 9 lines · Avi Kivity
Quoted 8 lines · Jan Kiszka

From: Jan Kiszka<[email protected]>

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

(quoted diff) +0 -0
@@ -1609,18 +1609,18 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm
 *kvm, u32 id)
Quoted 8 lines

Review static int kvm_vm_ioctl_create_vcpu(struct kvm · line 1614

Quoted 5 lines
(quoted diff) +1 -1
      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 <[email protected]>

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 <[email protected]>
---
 arch/x86/kvm/x86.c  |    5 -----
 virt/kvm/kvm_main.c |   11 ++++++-----
 2 files changed, 6 insertions(+), 10 deletions(-)
arch/x86/kvm/x86.c +0 -5
index 1d5a7f4..9826d5d 100644
@@ -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;
 }
virt/kvm/kvm_main.c +6 -5
index 5814645..57b173c 100644
@@ -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;
 }
Signature · 1 line
1.7.1