[PATCH] kvm: fix coalesced_mmio leak on shutdown

[PATCH] kvm: fix coalesced_mmio leak on shutdown

[Gregory Haskins]

It would appear that we are invoking kfree() on the wrong pointer in the
destructor for the coalesced_mmio device.  This would result in a potential
leak during shutdown.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---

 virt/kvm/coalesced_mmio.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 5ae620d..03ea280 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -80,7 +80,10 @@ static void coalesced_mmio_write(struct kvm_io_device *this,
 
 static void coalesced_mmio_destructor(struct kvm_io_device *this)
 {
-	kfree(this);
+	struct kvm_coalesced_mmio_dev *dev =
+		(struct kvm_coalesced_mmio_dev *)this->private;
+
+	kfree(dev);
 }
 
 int kvm_coalesced_mmio_init(struct kvm *kvm)

Re: [PATCH] kvm: fix coalesced_mmio leak on shutdown

[Chris Wright]

* Gregory Haskins (ghaskins@novell.com) wrote:
> It would appear that we are invoking kfree() on the wrong pointer in the
> destructor for the coalesced_mmio device.  This would result in a potential
> leak during shutdown.

Happens to work and not leak:

struct kvm_coalesced_mmio_dev { 
        struct kvm_io_device dev;
        struct kvm *kvm;
        int nb_zones;
        struct kvm_coalesced_mmio_zone zone[KVM_COALESCED_MMIO_ZONE_MAX];
};

> Signed-off-by: Gregory Haskins <ghaskins@novell.com>
> ---
> 
>  virt/kvm/coalesced_mmio.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
> index 5ae620d..03ea280 100644
> --- a/virt/kvm/coalesced_mmio.c
> +++ b/virt/kvm/coalesced_mmio.c
> @@ -80,7 +80,10 @@ static void coalesced_mmio_write(struct kvm_io_device *this,
>  
>  static void coalesced_mmio_destructor(struct kvm_io_device *this)
>  {
> -	kfree(this);
> +	struct kvm_coalesced_mmio_dev *dev =
> +		(struct kvm_coalesced_mmio_dev *)this->private;

I think container_of() makes more sense here.

thanks,
-chris

Re: [PATCH] kvm: fix coalesced_mmio leak on shutdown

[Gregory Haskins]

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Chris Wright wrote:
> * Gregory Haskins (ghaskins@novell.com) wrote:
>   
>> It would appear that we are invoking kfree() on the wrong pointer in the
>> destructor for the coalesced_mmio device.  This would result in a potential
>> leak during shutdown.
>>     
>
> Happens to work and not leak:
>
> struct kvm_coalesced_mmio_dev { 
>         struct kvm_io_device dev;
>         struct kvm *kvm;
>         int nb_zones;
>         struct kvm_coalesced_mmio_zone zone[KVM_COALESCED_MMIO_ZONE_MAX];
> };
>
>   
Ah, yes.  That explains it.  Still sloppy, tho.

>> Signed-off-by: Gregory Haskins <ghaskins@novell.com>
>> ---
>>
>>  virt/kvm/coalesced_mmio.c |    5 ++++-
>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
>> index 5ae620d..03ea280 100644
>> --- a/virt/kvm/coalesced_mmio.c
>> +++ b/virt/kvm/coalesced_mmio.c
>> @@ -80,7 +80,10 @@ static void coalesced_mmio_write(struct kvm_io_device *this,
>>  
>>  static void coalesced_mmio_destructor(struct kvm_io_device *this)
>>  {
>> -	kfree(this);
>> +	struct kvm_coalesced_mmio_dev *dev =
>> +		(struct kvm_coalesced_mmio_dev *)this->private;
>>     
>
> I think container_of() makes more sense here.
>   

I was working on that patch when I noticed the "leak" above.  Figured I
should send the fix out first, in case my container_of patch is shot down.

Just polishing it up now.  Will send out soon.

-Greg


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Re: [PATCH] kvm: fix coalesced_mmio leak on shutdown

[Chris Wright]

* Gregory Haskins (gregory.haskins@gmail.com) wrote:
> Chris Wright wrote:
> > * Gregory Haskins (ghaskins@novell.com) wrote:
> >> It would appear that we are invoking kfree() on the wrong pointer in the
> >> destructor for the coalesced_mmio device.  This would result in a potential
> >> leak during shutdown.
> >
> > Happens to work and not leak:
> >
> > struct kvm_coalesced_mmio_dev { 
> >         struct kvm_io_device dev;
> >         struct kvm *kvm;
> >         int nb_zones;
> >         struct kvm_coalesced_mmio_zone zone[KVM_COALESCED_MMIO_ZONE_MAX];
> > };
> >
> >   
> Ah, yes.  That explains it.  Still sloppy, tho.

Definitely.

> >>  static void coalesced_mmio_destructor(struct kvm_io_device *this)
> >>  {
> >> -	kfree(this);
> >> +	struct kvm_coalesced_mmio_dev *dev =
> >> +		(struct kvm_coalesced_mmio_dev *)this->private;
> >>     
> >
> > I think container_of() makes more sense here.
> 
> I was working on that patch when I noticed the "leak" above.  Figured I
> should send the fix out first, in case my container_of patch is shot down.
> 
> Just polishing it up now.  Will send out soon.

Sounds good.

thanks,
-chris