linux-kernel - Re: [PATCH] s390/vfio_ap: fix memory leak in vfio

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Date:   Thu, 16 Mar 2023 09:35:50 -0400
From:   Anthony Krowiak <akrowiak@...ux.ibm.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, jjherne@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, borntraeger@...ux.ibm.com
Subject: Re: [PATCH] s390/vfio_ap: fix memory leak in vfio_ap device driver


On 3/16/23 4:39 AM, Heiko Carstens wrote:
> On Wed, Mar 15, 2023 at 11:39:32AM -0400, Tony Krowiak wrote:
>> The device release callback function invoked to release the matrix device
>> uses the dev_get_drvdata(device *dev) function to retrieve the
>> pointer to the vfio_matrix_dev object in order to free its storage. The
>> problem is, this object is not stored as drvdata with the device; since the
>> kfree function will accept a NULL pointer, the memory for the
>> vfio_matrix_dev object is never freed.
>>
>> Since the device being released is contained within the vfio_matrix_dev
>> object, the container_of macro will be used to retrieve its pointer.
>>
>> Fixes: 1fde573413b5 ("s390: vfio-ap: base implementation of VFIO AP device driver")
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_drv.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
>> index 997b524bdd2b..15e9de9f4574 100644
>> --- a/drivers/s390/crypto/vfio_ap_drv.c
>> +++ b/drivers/s390/crypto/vfio_ap_drv.c
>> @@ -54,8 +54,9 @@ static struct ap_driver vfio_ap_drv = {
>>   
>>   static void vfio_ap_matrix_dev_release(struct device *dev)
>>   {
>> -	struct ap_matrix_dev *matrix_dev = dev_get_drvdata(dev);
>> -
>> +	struct ap_matrix_dev *matrix_dev = container_of(dev,
>> +							struct ap_matrix_dev,
>> +							device);
>>   	kfree(matrix_dev);
> Could you keep this code more readable, including adding the missing
> blank line after the declaration, please? Something like:
>
> static void vfio_ap_matrix_dev_release(struct device *dev)
> {
> 	struct ap_matrix_dev *matrix_dev;
>
> 	matrix_dev = container_of(dev, struct ap_matrix_dev, device);
> 	kfree(matrix_dev);
> }
>
> Thanks!


Will do.