linux-kernel - Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP device driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <6ff0eac2-7c0f-4ab1-6301-c7f6997be591@linux.ibm.com>
Date:   Thu, 14 Jun 2018 09:04:12 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     pmorel@...ux.ibm.com, Cornelia Huck <cohuck@...hat.com>
Cc:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP
 device driver

On 06/13/2018 08:16 AM, Pierre Morel wrote:
> On 13/06/2018 14:12, Cornelia Huck wrote:
>> On Wed, 13 Jun 2018 14:01:54 +0200
>> Pierre Morel <pmorel@...ux.ibm.com> wrote:
>>
>>> On 13/06/2018 13:14, Cornelia Huck wrote:
>>>> On Wed, 13 Jun 2018 12:54:40 +0200
>>>> Pierre Morel <pmorel@...ux.ibm.com> wrote:
>>>>> On 13/06/2018 09:48, Cornelia Huck wrote:
>>>>>> On Wed, 13 Jun 2018 09:41:16 +0200
>>>>>> Pierre Morel <pmorel@...ux.ibm.com> wrote:
>>>>>>> On 07/05/2018 17:11, Tony Krowiak wrote:
>>>>>>>> Introduces a new AP device driver. This device driver
>>>>>>>> is built on the VFIO mediated device framework. The framework
>>>>>>>> provides sysfs interfaces that facilitate passthrough
>>>>>>>> access by guests to devices installed on the linux host.
>>>>>>> ...snip...
>>>>>>>> +static int vfio_ap_matrix_dev_create(void)
>>>>>>>> +{
>>>>>>>> +    int ret;
>>>>>>>> +
>>>>>>>> +    vfio_ap_root_device = 
>>>>>>>> root_device_register(VFIO_AP_ROOT_NAME);
>>>>>>>> +
>>>>>>>> +    if (IS_ERR(vfio_ap_root_device)) {
>>>>>>>> +        ret = PTR_ERR(vfio_ap_root_device);
>>>>>>>> +        goto done;
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>> +    ap_matrix = kzalloc(sizeof(*ap_matrix), GFP_KERNEL);
>>>>>>>> +    if (!ap_matrix) {
>>>>>>>> +        ret = -ENOMEM;
>>>>>>>> +        goto matrix_alloc_err;
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>> +    ap_matrix->device.type = &vfio_ap_dev_type;
>>>>>>>> +    dev_set_name(&ap_matrix->device, "%s", VFIO_AP_DEV_NAME);
>>>>>>>> +    ap_matrix->device.parent = vfio_ap_root_device;
>>>>>>>> +    ap_matrix->device.release = vfio_ap_matrix_dev_release;
>>>>>>>> +    ap_matrix->device.driver = &vfio_ap_drv.driver;
>>>>>>>> +
>>>>>>>> +    ret = device_register(&ap_matrix->device);
>>>>>>>> +    if (ret)
>>>>>>>> +        goto matrix_reg_err;
>>>>>>>> +
>>>>>>>> +    goto done;
>>>>>>>> +
>>>>>>>> +matrix_reg_err:
>>>>>>>> +    put_device(&ap_matrix->device);
>>>>>>> Did not see this before but here you certainly want to
>>>>>>> do a kfree and not a put_device.
>>>>>> No, this must not be a kfree. Once you've tried to register 
>>>>>> something
>>>>>> embedding a struct device with the driver core, you need to use
>>>>>> put_device, as another path may have acquired a reference, even if
>>>>>> registering ultimately failed. See the comment for 
>>>>>> device_register().
>>>>>> IOW, the code is correct.
>>>>> learned something again :) ,
>>>>> but still, a kfree is needed for the kzalloc.
>>>>> Does'nt it?
>>>> No, the put callback for the embedding structure needs to take care of
>>>> freeing things. Otherwise it is buggy.
>>> Seems buggy to me.
>>> How does the put_device knows if it is embedded and then in what it is
>>> embedded ?
>> It does not need to know; the code registering the structure needs to
>> set up device->release correctly.
>
> yes right, thanks.

See the vfio_ap_matrix_dev_release() callback.

>
>
>>
>>>>>>>> +
>>>>>>>> +matrix_alloc_err:
>>>>>>>> +    root_device_unregister(vfio_ap_root_device);
>>>>>>>> +
>>>>>>>> +done:
>>>>>>>> +    return ret;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static void vfio_ap_matrix_dev_destroy(struct ap_matrix 
>>>>>>>> *ap_matrix)
>>>>>>>> +{
>>>>>>>> +    device_unregister(&ap_matrix->device);
>>>>>>>> +    root_device_unregister(vfio_ap_root_device);
>>>>>>> Also here you need a kfree(ap_matrix) too .
>>>>>> Same here.
>>>
>