linux-kernel - Re: [PATCH] s390/vfio-ap: Fix module unload memory leak of matrix

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Message-ID: <4ea3de71-9d68-59c6-bfb8-d8258019e585@linux.ibm.com>
Date:   Fri, 18 Jun 2021 10:35:21 -0400
From:   "Jason J. Herne" <jjherne@...ux.ibm.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        pasic@...ux.ibm.com, akrowiak@...ux.ibm.com
Subject: Re: [PATCH] s390/vfio-ap: Fix module unload memory leak of matrix_dev

On 6/18/21 10:10 AM, Jason Gunthorpe wrote:
> On Fri, Jun 18, 2021 at 09:35:24AM -0400, Jason J. Herne wrote:
>> vfio_ap_matrix_dev_release is shadowing the global matrix_dev with driver
>> data that never gets set. So when release is called we end up not freeing
>> matrix_dev. The fix is to remove the shadow variable and just free the
>> global.
> 
> I would clarify this commit message to say that the drv_data of the
> matrix_dev is never set and so dev_get_drvdata() always returns NULL
> 
> And I would suggest to use
> 
>    container_of(dev, struct ap_matrix_dev, dev)
> 
> instead of the global variable, and probably NULL the global
> too..
> 

The use of driver_data seems to have been completely erroneous here. In this
case the global matrix_dev is the top level struct. It is not contained in
anything. matrix_dev is created upon module load, and it is freed when the
module exits.

So I don't think using container_of makes sense. Unless I've
misunderstood your suggestion?

-- 
-- Jason J. Herne (jjherne@...ux.ibm.com)